External flash control system

ABSTRACT

A flash control system remotely controls an external flash by a camera. In the camera, a stop value is calculated as a photographic exposure factor for the external flash, and a flash-light emission timing of the external flash is calculated. A built-in flash of the camera is controlled to emit two light signals at a time interval representing the stop value. The external flash detects the two light signals. A timing of a flash-light emission of the external flash is controlled in accordance with one of the two light signals. An amount of the flash-light emission of the external flash is controlled in accordance with the time interval.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a flash control system for remotelycontrolling a flash-light emission of an external flash device by alight signal output from a camera associated with the external flashdevice.

2. Description of the Related Art

Conventionally, a flash-light emission of an external flash device isremotely controlled by a camera in accordance with a so-called slavemethod. Namely, when a flash light is emitted from a built-in flashdevice of the camera, the emitted flash light serves as a trigger forinitiating an flash-light emission of the external flash device.

In this external flash control system, an amount of the flash-lightemission of the external flash device cannot be accurately controlled,because only a timing of the flash-light emission of the external flashdevice is adjusted, with the amount of the flash-light emission beingfixed. Thus, it is difficult to provide highly accurate exposure inresponse to photographing conditions which are variable depending on anobject-distance or the like.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a flashcontrol system for remotely controlling a flash-light emission of anexternal flash device by a light signal output from a camera, in whichboth a timing and an amount of the flash-light emission are properly andaccurately controllable.

In accordance with an aspect of the present invention, there is provideda flash control system for remotely controlling an external flash deviceby a camera associated with the external flash device. In the flashcontrol system, the camera includes a stop value calculator thatcalculates a stop value as an exposure factor for the external flashdevice, a light signal source that emits a light signal, and a lightsignal controller that controls the light signal source to emit at leasttwo light signals therefrom at a time interval such that the stop valueis represented by the time interval between the two light signals. Theexternal flash device includes a light signal detector that detects thetwo light signals emitted from the light signal source, and aflash-light emission controller that controls an amount of theflash-light emission of the external flash device in accordance with thetime interval between the two light signals.

Preferably, in the flash control system, the camera further includes aflash-light emission timing calculator that calculates a flash-lightemission timing at which a flash-light should be emitted from theexternal flash device. In this case, the light signal controller furthercontrols an emission of one of the two light signals such that theflash-light emission timing is represented by the emission of the one ofthe two light signals, and the flash-light emission controller furthercontrols a timing of the flash-light emission of the external flashdevice in accordance with the emission of the one of the two lightsignals. Preferably, the control of the timing of the flash-lightemission of the external flash device by the flash-light emissioncontroller is based on a last light signal of the two light signals.

The calculation of the stop value by the stop value calculator may bebased on at least a photometry measurement performed by the camera uponphotographing. Also, the light signal source may comprise a flash lampof a built-in flash device incorporated in the camera.

Preferably, the flash-light emission controller includes a lightdetector that detects the flash-light emission of the external flashdevice as a reflected light, a first processor that processes thereflected light, detected by the light detector, to produce a firstlight-quantitative data representing an amount of the reflected light, asecond processor that processes the time interval to produce a secondlight-quantitative data deriving from the stop value, and a comparatorthat compares the first light-quantitative data with the secondlight-quantitative data, such that the flash-light emission of theexternal flash device is stopped when it is determined by the comparatorthat the first-quantitative data coincides with the secondlight-quantitative data. The light detector may comprise the lightsignal detector for detecting the two light signals.

In accordance with another aspect of the present invention, there isprovided an external flash device, which comprises a flash lamp thatemits a flash-light, a light signal detector that detects two lightsignals emitted at a time interval rep-resenting a stop value as aphotographic exposure factor, and a flash-light emission controller thatcontrols an amount of a flash-light emission of the flash lamp inaccordance with the time interval between the two light signals.

Preferably, the external flash device further comprises a timingcontroller that controls a timing of the flash-light emission of theflash lamp on the basis of a detected-timing at which one of the twolight signals is detected by the light signal detector. Preferably, thecontrol of the timing of the flash-light emission of the flash lamp bythe flash-light emission controller is based on a last light signal ofthe at least two light signals.

Preferably, the flash-light emission controller includes a lightdetector that detects the flash-light emission of the external flashdevice as a reflected light, a first processor that processes thereflected light, detected by the light detector, to produce a firstlight-quantitative data representing an amount of the reflected light, asecond processor that processes the time interval to produce a secondlight-quantitative data deriving from the stop value, and a comparatorthat compares the first light-quantitative data with the secondlight-quantitative data, such that the flash-light emission of the flashlamp is stopped when it is determined by the comparator that thefirst-quantitative data coincides with the second light-quantitativedata. The light detector may comprise the light signal detector fordetecting the at least two light signals.

In accordance with yet another aspect of the present invention, there isprovided a camera, which comprises a stop value calculator thatcalculates a stop value as a photographic exposure factor for anexternal flash device, a light signal source that emits a light signalto the external flash device; and a light signal controller thatcontrols the light signal source to emit at least two light signalstherefrom at a time interval such that the stop value is represented bythe time interval between the at least two light signals.

Preferably, the camera further comprises a flash-light emission timingcalculator that calculates a flash-light emission timing at which aflash-light should be emitted from the external flash device. In thiscase, the light signal controller further controls the emission of theat least two light signals such that the flash-light emission timing isrepresented by an emission of one of the at least two light signals.Preferably, the control of the emission of the at least two lightsignals by the light signal controller is performed such that theflash-light emission timing is represented by an emission of a lastlight signal of the at least two light signals.

When the camera comprises a lens shutter type camera, a timing of theemission of the last light signal of the at least two light signalscoincides with a time at which an aperture of a shutter of the lensshutter type camera reaches a maximum aperture during an opening-actionof the shutter.

When the camera comprises a single lens reflex type camera, a timing ofan emission of a first light signal of the at least two light signalscoincides with a time, at which a leading shutter curtain of afocal-plane shutter of the single lens reflex type camera reaches an endposition thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The object and other objects of the present invention will be betterunderstood from the following description, with reference to theaccompanying drawings, in which:

FIG. 1 is a perspective view schematically showing a situation in whichan object is photographed by a lens shutter (LS) camera, using anexternal flash device, in accordance with a first embodiment of a flashcontrol system of the present invention;

FIG. 2 is a schematic block diagram of the LS camera;

FIG. 3 is a part of a wiring diagram of the external flash device;

FIG. 4 is the remaining part of the wiring diagram of the external flashdevice;

FIG. 5 is a timing chart showing a control of both a timing and anamount of a flash-light emission of the external flash device accordingto the first embodiment of the flash control system of the presentinvention;

FIG. 6 is a flowchart of a main control routine executed in a systemcontrol circuit of the LS camera;

FIG. 7 is a part of a flowchart of a photographing operation routineexecuted in the main routine of FIG. 6;

FIG. 8 is the remaining part of the flowchart of the photographingoperation routine executed in the main routine of FIG. 6;

FIG. 9 is a flowchart of a pre-charging routine executed in the executedin the main routine of FIG. 6;

FIG. 10 is a flowchart of an additional-charging routine executed in thephotographing operation routine of FIGS. 7 and 8;

FIG. 11 is a flowchart of an AE calculation routine executed in thephotographing operation routine of FIGS. 7 and 8;

FIG. 12 is a flowchart of an FM calculation routine executed in thephotographing operation routine of FIGS. 7 and 8;

FIG. 13 is a graph conceptually showing a variation in an aperture of ashutter of the LS camera;

FIG. 14 is a table based on the graph of FIG. 13;

FIG. 15 is a part of a flowchart of an exposure-controlling routineexecuted in the photographing operation routine of FIGS. 7 and 8;

FIG. 16 is the remaining part of the flowchart of theexposure-controlling routine executed in the photographing operationroutine of FIGS. 7 and 8;

FIG. 17 is a graph showing a relationship between a stop value of theshutter, at which a flash-light emission of a built-in flash device ofthe LS camera is started, and a trigger time, at which the flash-lightemission of the built-in flash device is triggered;

FIG. 18 is a table showing relationships between parameters forcontrolling the amount of the flash-light emission of the external flashdevice;

FIG. 19 is a flowchart of a timer-interruption routine executed in thephotographing operation routine of FIGS. 7 and 8;

FIG. 20 is a part of a flowchart of a main routine executed in a CPU ofthe external flash device;

FIG. 21 is the remaining part of the flowchart of the main routineexecuted in the CPU of the external flash device;

FIG. 22 is a flowchart of a 125 ms-interruption routine executed in themain routine of FIGS. 20 and 21;

FIG. 23 is a part of a flowchart of a P7-interruption routine executedin the main routine of FIGS. 20 and 21;

FIG. 24 is the remaining part of the flowchart of the P7-interruptionroutine executed in the main routine of FIGS. 20 and 21;

FIG. 25 is a perspective view schematically showing a situation in whichan object is photographed by a single lens reflex (SLR) type camera,using an external flash device, in accordance with a second embodimentof a flash control system of the present invention;

FIG. 26 is a schematic block diagram of the SLR camera;

FIG. 27 is a flowchart of a main control routine executed in a systemcontrol circuit of the SLR camera;

FIG. 28 is a part of a flowchart of a photographing operation routineexecuted in the main routine of FIG. 27;

FIG. 29 is the remaining part of the flowchart of the photographingoperation routine executed in the main routine of FIG. 27;

FIG. 30 is a part of a flowchart of an exposure-calculation routineexecuted in the photographing operation routine of FIGS. 28 and 29;

FIG. 31 is the remaining part of the flowchart of theexposure-calculation routine executed in the photographing operationroutine of FIGS. 28 and 29;

FIG. 32 is a part of a flowchart of an exposure-controlling routineexecuted in the photographing operation routine of FIGS. 28 and 29;

FIG. 33 is another part of the flowchart of the exposure-controllingroutine executed in the photographing operation routine of FIGS. 28 and29; and

FIG. 34 is the remaining part of the flowchart of theexposure-controlling routine executed in the photographing operationroutine of FIGS. 28 and 29.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a situation in which an object A (person) isphotographed by a camera 10, using an external flash device 100, and aflash-light-emission of the external flash device 100 is controlled by afirst embodiment of a flash-control system according to the presentinvention. The camera 10 is formed as a lens-shutter (LS) type camera inwhich a shutter is incorporated in a photographing lens system.

As well known, in the LS type camera 10, the shutter comprises aplurality of blades which are radially and movably arranged so as todefine continuously varying apertures. The shutter is usually closed,and thus no aperture is defined by the blades. While a photographingoperation is performed, the shutter is opened by moving the blades suchthat an aperture of the shutter is gradually increased toward a givenstop value. As soon as the aperture reaches the given stop value, theshutter is closed. Thus, the photographing operation can be executedwith a proper exposure.

The camera 10 has an internal flash device or built-in flash device, andthe built-in flash device is associated with a flash-window 16 providedin a front of a camera body 10 a of the camera 10. Of course, when thebuilt-in flash device is electrically activated, a flash-light isemitted through the flash-window 16. According to the present invention,a flash-light emission of the built-in flash device is also utilized toremotely control the external flash device 100 in a manner as stated indetail hereinafter.

As shown in FIG. 1, the camera 10 has a viewfinder window 18 and aphotometry/distance measurement window 20 provided in the front of thecamera body 10 a. Of course, the viewfinder window 18 is formed as apart of a viewfinder optical system, and the photometry/distancemeasurement window 20 is associated with both a photometry measurementsensor and an object-distance measurement sensor.

The camera 10 also has a lens barrel 23 provided in the front of thecamera body 10 a and containing the photographing lens system, generallyindicated by reference 24. The lens barrel 23 is movable between aretracted position, in which the lens barrel 23 is received in thecamera body 10 a, as shown in FIG. 1, and a projected position, in whichthe lens barrel 23 is moved from the retracted position. Of course, whena photographing operation is performed, the lens barrel 23 is at theprojected position.

The camera 10 is provided with a power ON/OFF switch button 13, arelease switch button 12 and a flash-mode selection switch button 11,and these switch buttons 13, 12 and 11 are suitably arranged on a top ofthe camera body 10 a.

The power ON/OFF switch button 13 is formed as a transfer-type switchbutton, which is shiftable between an ON-side and an OFF-side. Byshifting the power ON/OFF switch button 13 to the ON-side, the camera 10is brought into a photographing-operation-enabling state, and, byshifting the power ON/OFF switch button 13 to the OFF-side, the camera10 is brought into a photographing-operation-disabling state.

The release switch button 12 is formed as a self-return type switchbutton, which is manipulated in a two-step depression manner. Namely,when the release switch button 12 is partly depressed, a photometrymeasurement and an object-distance measurement are performed, and, whenthe release switch button 12 is fully depressed, a photographingoperation is performed.

The flash-mode selection switch button 11 is also formed as aself-return switch button. By manipulating the flash-mode selectionswitch button 11, it is possible to select one of an automatic internalflash mode, an internal flash-OFF mode, an internal flash-ON mode and anexternal flash-ON mode. Namely, a selection of each individual flashmode is sequentially and cyclically switched in a given order by-everydepressing of the flash-mode selection switch button 11. Note, in thesituation as shown in FIG. 1, the external flash-ON mode is selected.

In the situation shown in FIG. 1, the external flash device 100 isutilized in a so-called wireless mode in which the external flash device100 is separated from the camera 10. However, the external flash device100 may be optionally utilized in a so-called clip-on mode in which theexternal flash device 100 is mounted on the top of the camera body 10 a.To this end, a mount 14 for mounting the external flash device 100 onthe camera 10 is provided in the top of the camera body 10 a, and theexternal flash device 100 has a mount foot 150 which is detachablyconnected to the mount 14.

The external flash device 100 has a power ON/OFF switch button 154 and amode selection switch button 152 provided on at a top of a body 100 athereof. Of course, the external flash device 100 is electricallypowered ON by a turn-ON of the power ON/OFF switch button 154, and iselectrically powered OFF by a turn-OFF of the power ON/OFF switch button154. The mode selection switch button 152 is formed as a self-returntype switch button. By manipulating the mode selection switch button152, either the wireless mode or the clip-on mode is selected. Namely, aselection of each mode is alternately switched by every depressing ofthe mode selection switch button 152. Note, in the situation as shown inFIG. 1, the wireless mode is selected.

Also, the external flash device 100 has a flash window 159 provided on afront of the body 100 a thereof, and the flash window 159 is associatedwith a flash lamp, such as a xenon lamp, contained in the body 100 a.When the flash lamp is electrically energized, the flash-light isemitted from the flash lamp through the flash window 159. Further, theexternal flash device 100 has a light receiver 155 provided in the frontof the body 100 a thereof, and the light receiver 155 includes aphoto-sensor, such as a photo-transistor.

When a photographing operation is performed in the situation as shown inFIG. 1, i.e. when the external flash-ON mode and the wireless mode areselected in the camera 10 and the external flash device 100,respectively, the built-in flash device of the camera 10 is used as alight-signal-producing source for controlling both an amount offlash-light-emission and a flash-timing of the external flash device100.

When the release switch button 12 is partly depressed, an exposurefactor for obtaining a proper exposure by a flash-light-emission of theexternal flash device 100 is calculated on the basis of a photometrymeasurement and an object-distance measurement performed by the partialdepression of the release switch button 12. Then, when the releaseswitch button 12 is fully depressed, an opening-action of the shutter isstarted. In the first embodiment, during the opening-action of theshutter, a light-pulse signal is twice emitted from the built-in flashdevice of the camera 10 to the external flash device 100 such that thecalculated exposure factor, which determines an amount of a flash-lightto be emitted from the external flash device 100, is represented by atime interval between the twice-emitted light-pulse signals, i.e. thefirst light-pulse signal and the second light-pulse signal, and suchthat the second light-pulse signal serves as a flash-timing signal forinitiating a flash-light emission of the external flash device 100.

The first and second light-pulse signals, emitted from the built-inflash device, are made incident on the object A, and are then reflectedtoward the external flash device 100, as shown by a double-chained linein FIG. 1. The reflected light-pulse signals are received by the lightreceiver 155 of the external flash device 100, and are then processedsuch that a flash-light emission of the external flash device 100 isinitiated upon receiving the second light-pulse signal, and such thatthe flash-light emission of the external flash device 100 is continueduntil a total amount of the flash-light-emission reaches a valuecalculated on the basis of the exposure factor, represented by the timeinterval between the first light-pulse signal and the second light-pulsesignal.

Note, if necessary, the first light-pulse signal may be utilized as theflash-timing signal for the flash-light emission of the external flashdevice 100. Of course, in this case, the flash-light emission of theexternal flash device 100 is initiated after a given time period haselapsed from a time at which the second light-pulse signal is receivedby the light receiver 155.

FIG. 2 schematically shows a block diagram of the camera 10. The camera10 is provided with a system control circuit 40, which may beconstituted as a microcomputer, used to control the camera 10 as awhole, comprising, for example, a central processing unit (CPU), aread-only memory (ROM) for storing programs and constants, arandom-access memory (RAM) for storing temporary data, and aninput/output interface circuit (I/O).

The system control circuit 40 is electrically powered by a battery 70,and the power ON/OFF switch button 13, formed as a transfer-type switchbutton, is associated with a power ON/OFF switch 13 a, which is turnedON by shifting the power switch button 13 to the ON-side, and which isturned OFF by shifting the power switch button 13 to the OFF-side. Aslong as the battery 70 is in an active state, it is monitored by thesystem control circuit 40 whether the camera 10 is in thephotographing-operation-enabling state (i.e. ON-state) or thephotographing-operation-disabling state (i.e. OFF-state) by the turn-ONand the turn-OFF of the power ON/OFF switch 13 a.

In particular, when the power ON/OFF switch 13 a is turned ON, the lensbarrel 23 is moved from the retracted position (FIG. 1) to the projectedposition, whereby the camera 10 is set in thephotographing-operation-enabling state. When the power ON/OFF switch 13a is turned OFF, the lens barrel 23 is returned from the projectedposition to the retracted position (FIG. 1), whereby the camera 10 isset in the photographing-operation-disabling state.

In FIG. 2, the built-in flash device, associated with the flash-window16, is generally indicated by reference 16′, and is electrically poweredby the battery 70. The built-in flash device 16′ includes a flash lamp16 c, such as a xenon lamp, a main capacitor 16 b for electricallyenergizing the flash lamp 16 c, and a step-up transformer circuit 16 afor increasing an output voltage of the battery 70 to develop a voltagehigh enough to electrically charge the main capacitor 16 b.

The built-in flash device 16′ also includes a flash-light-emissioncontrol circuit 16d for controlling the energization of the flash lamp16 c, i.e. a turn-ON and a turn-OFF of the flash lamp 16 c. For example,the flash-light-emission control circuit has an insulated-gate bipolartransistor (IGBT) incorporated therein, and the control of theenergization of the flash lamp 16c is performed by switching ON and OFFthe IGBT.

Further, the built-in flash device 16′ includes a charge-voltagedetector circuit 16 e for detecting a charge voltage of the maincapacitor 16 b, and the charge-voltage detector circuit 16 e outputs asignal representing the charge voltage of the main capacitor 16 b. Theoutput signal is retrieved, as a charge voltage data, by the systemcontrol circuit 40, such that the charging of the main capacitor 16 b isproperly controlled.

Note, the main capacitor 16 b must be charged to, for example, 270volts, before the xenon lamp 16 c can be electrically energized so as toemit a flash-light therefrom. Namely, 270 volts represents a minimumvoltage at which the xenon lamp 16 c can emit a flash-light.

In FIG. 2, reference 36 indicates a back-cover switch for detectingwhether a back-cover of the camera body 10 a is opened or closed. Whenthe back-cover is closed, the switch 36 is turned ON, and, when theback-cover is opened, the switch 36 is turned OFF. By detecting a changeof the state of the back-cover switch 36, it is possible to determinewhether a film cartridge has been loaded in the camera 10. Namely, whenthe back-cover switch 36 is changed from the OFF-state to the ON-state,it is possible to reckon that the loading of the film cartridge has beenperformed.

The back-cover switch 36 is associated with a DX code detector circuit26. When the back-cover switch 36 is changed from the OFF-state to theON-state, i.e. when a film cartridge is loaded in the camera 10, a DXcode data, which represents a sensitivity of a photographic filmconcerned, is read from the loaded film cartridge by the DX codedetector circuit 26, and is then retrieved by the system control circuit40.

Also, the back-cover switch 36 is associated with a driver circuit 42for driving a film-feeding motor M1, and the driver circuit 42 isoperated under control of the system control circuit 40. When theloading of the film cartridge, i.e. the change of the back-cover switch36 from the OFF-state to the ON-state is detected by the system controlcircuit 40, the driver circuit 42 is operated, thereby driving thefilm-feeding motor M1 such that the film is drawn out of the filmcartridge by a predetermined length, and thus a first frame of the filmis positioned onto a photographing plane.

Of course, whenever a photographing operation is completed, thefilm-feeding motor M1 is automatically driven by the driver circuit 42such that the film is fed from the film cartridge by a lengthcorresponding to one frame. Namely, the camera 10 is provided with afilm-feeding detector circuit 28 for detecting a feeding of one frame ofthe film. When the feeding of one frame of the film is detected by thefilm-feeding detector circuit 28, the driving of the film-feeding motorM1 is stopped.

In FIG. 2, reference 34 indicates a film-rewinding switch, and thisswitch 34 is operated by a film-rewinding switch button, which may beprovided in a bottom of the camera body 10 a. The film-rewinding switch34 is associated with the driver circuit 42 for driving the film-feedingmotor M1. When the film-rewinding switch 34 is turned ON, thefilm-feeding motor M1 is reversely driven such that the film is forciblyrewound in the film cartridge. Further, after the last frame of the filmis exposed by a photographing operation, the film-feeding motor M1 isreversely driven for rewinding all the film in the film cartridge. Note,it is detected by the film-feeding detector circuit 28 whether therewinding of the film is completed.

The release switch button 12 is associated with both a photometrymeasurement switch 12 a and a release switch 12 b. Namely, when therelease switch button 12 is partly depressed, the photometry measurementswitch 12 a is turned ON, and, when the release switch button 12 isfully depressed, the release switch 12 b is turned ON.

The photometry measurement switch 12 a is associated with both aphotometry measurement circuit 22 and a distance measurement circuit 21containing the aforesaid photometry measurement sensor and the aforesaiddistance measurement sensor, respectively, associated with thephotometry/distance measurement window 20. The photometry measurementcircuit 22 detects an intensity of light, reflected from the object A(FIG. 1), through the window 20, thereby producing a luminance signalrepresenting a luminance of the object A. The distance measurementcircuit 22 detects an object-distance to the object A, thereby producingan object-distance signal representing the object-distance to the objectA. The respective luminance signal and object-distance signal aresuitably retrieved as a luminance data and an object-distance data bythe system control circuit 40, in which a proper exposure value data iscalculated on the basis of the luminance data, the object-distance dataand the DX code data.

The release switch 12 b is associated with a driver circuit 44 fordriving a focusing motor M2, and the driver circuit 44 is operated undercontrol of the system control circuit 40 to drive the focusing motor M2,which is associated with an automatic focusing mechanism incorporated inthe photographing lens system 24. When the release switch 12 b is turnedON, the automatic focusing mechanism is actuated by driving the motor M2such that the photographing lens system 24 is moved from an initialposition in accordance with the object-distance data, obtained from thedistance measurement circuit 21, until the object A is focused on thephotographing plane defined in the camera 10.

Further, the release switch 12 b is associated with a driver circuit 46for driving a shutter motor M3, and the driver circuit 46 is operatedunder control of the system control circuit 40 to drive the shuttermotor M3, which is associated with the shutter incorporated in thephotographing lens system 24. When the release switch 12 b is turned ON,the shutter is actuated by the shutter motor M3 such that aphotographing operation is performed with a given exposure timedetermined on the basis of the calculated proper exposure value. Namely,during the photographing operation, the shutter is opened and closed bythe shutter motor M3 such that the given exposure time can be obtained.

The shutter is associated with a shutter switch 32. When the shutter isin an initial-state or closed-state, no aperture is defined by theblades. When an opening-action of the shutter is started, the shutterswitch 32 is turned ON. The opening-action of the shutter is continueduntil an aperture reaches a given stop value, and then the shutter isclosed. When the aperture of the shutter is completely closed, theshutter switch 32 is turned OFF. The ON-state and OFF-state of theshutter switch 32 is monitored by the system control circuit 40 tocontrol the driving of the shutter motor M3.

The flash-mode selection switch button 11 is associated with aflash-mode selection switch 11 a, which is turned ON by a depression ofthe flash-mode selection switch button 11. As mentioned above, bymanipulating the flash-mode selection switch button 11, one of theautomatic internal flash mode, the internal flash-OFF mode, the internalflash-ON mode and the external flash-ON mode is selected. Namely, aselection of each individual flash mode is sequentially and cyclicallyswitched in a given order by every turning ON of the flash-modeselection switch 11 a.

In FIG. 2, reference 30 indicates a liquid crystal display (LCD) 30which is provided in a suitable location of the camera body 10 a. TheLCD 30 is operated under control of the system control circuit 40, anddisplays various messages regarding a selected flash mode, a number offrames of a loaded film cartridge and so on.

Also, in FIG. 2, respective references 62 and 64 indicate a red lamp anda green lamp, each of which is provided in a suitable location on thecamera body 10 a. Each of the red and green lamps 62 and 64 is suitablylit or blinked ON and OFF to announce a predetermined message, as statedin detail hereinafter.

When either the automatic internal flash mode or the internal flash-ONmode is selected by manipulating the flash-mode selection switch button11, i.e. when a photographing operation is performed by emitting aflash-light from the built-in flash device 16′ for the purpose ofexposure, a first stop value, corresponding to a flash-light-emissionaperture, is calculated by the system control circuit 40 on the basis ofa photographic film sensitivity data (DX code data) obtained from the DXcode detector circuit 26, an object-distance data obtained from theobject-distance measurement circuit 21, and a charge voltage data of themain capacitor 16 b obtained from the detector circuit 16 e.

Note, the flash-light-emission aperture is defined as an aperture of theshutter at which a flash-light emission of the built-in flash device 16′is started during an opening-action of the shutter in the automaticinternal flash mode or the internal flash-ON mode.

Also, in the system control, circuit 40, a duration of shutter-open timeis calculated on the basis of an exposure value as calculated in theaforesaid manner. Note, the duration of shutter-open time is defined asa duration of time counted from a time, at which an opening-action ofthe shutter is started, to a time, at which a closing-action of theshutter is started.

After the calculations of the first stop value and duration ofshutter-open time, the shutter motor M3 is driven by the driver circuit46, whereby an opening-action of the shutter is started at a constantspeed. When an aperture of the shutter reaches the calculatedflash-light-emission aperture, a flash-light is immediately emitted fromthe built-in flash device 16′. Thereafter, when the calculated durationof shutter-open time has elapsed, the shutter motor M3 is reverselydriven so that a closing-action of the shutter is started at a higherspeed than the opening-action of the shutter. Thus, it is possible toachieve the photographing operation with a proper exposure by utilizingthe built-in flash lamp 16′.

When the external flash-ON mode and the wireless mode are selected inthe camera 10 and the external flash device 100, respectively, i.e whena photographing operation is performed by emitting a flash-light fromthe external flash device 100 for the purpose of exposure (FIG. 1), asecond stop value, corresponding to a maximum aperture determined by anexposure value as calculated in the aforesaid manner, is calculated bythe system control circuit 40, and a flash-light emission of theexternal flash device 100 is started at the second stop value.

Thereafter, the shutter motor M3 is driven by the driver circuit 46,whereby an opening-action of the shutter is started at a constant speed.During the opening-action of the shutter, a flash-light is twice emittedas a light-pulse signal from the built-in flash device 16′ on the basisof the calculated second stop value, such that the second stop value isrepresented by a time interval between the twice-emitted light-pulsesignals: the first light-pulse signal and the second light-pulse signal,and such that the second light-pulse signal serves as a flash-timingsignal for initiating a flash-light-emission of the external flashdevice 100. In short, the second stop value is transmitted to theexternal flash device 100 as the exposure factor for obtaining theproper exposure by the flash-light-emission of the external flash device100.

As already stated, the first and second light-pulse signals, emittedfrom the built-in flash device 16′, are received by the light receiver155 of the external flash device 100, and are then processed such that aflash-light-emission of the external flash device 100 is initiated uponreceiving the second light-pulse signal, and such that theflash-light-emission of the external flash device 100 is continued untila total amount of the flash-light-emission reaches a value representedby the exposure factor or time interval between the first light-pulsesignal and the second light-pulse signal. Note, in the first embodiment,of course, the second light-pulse signal is emitted from the built-inflash device 16′ when an aperture of the shutter reaches the maximumaperture corresponding to the second stop value.

FIGS. 3 and 4 show a wiring diagram of the external flash device 100.Note, respective terminals a, b, c and d shown in FIG. 3 are connectedto terminals a, b, c and d shown in FIG. 4. The wiring diagram shown inFIGS. 3 and 4 may be sectioned into five sections indicated byreferences G1, G2, G3, G4 and G5, respectively.

The respective power ON/OFF switch button 154 and mode selection switchbutton 152, shown in FIG. 1, are associated with a power ON/OFF switch154 a and a mode selection switch 152 a included in the section G4.Also, the xenon lamp contained in the body 100 a of the external flashdevice 100 is indicated by reference 115 in the section G3, and thephoto-transistor included in the light receiver 155 is indicated byreference 138 in the section G5. A main capacitor 109 for electricallyenergizing the xenon lamp 115 is arranged and illustrated between thesections G2 and G3, and a detachable battery 106 for electricallypowering the external flash device 100 is included in the section G1.

The section G4 forms a controller for controlling the external flashdevice 100 as a whole. The controller G4 includes a central processingunit (CPU) 123 and peripheral elements thereof. As shown in FIG. 4, theCPU 123 has a plurality of ports indicated by references P_(a), P1,P_(ad), P2, P_(int), P3, P4, P5, P6, P7, P_(da), P8, P_(b) and P_(c).

Each of the ports P1, P2, P4, P5 and P6 is formed as an output port,from which either a high level signal [1] or a low level signal [0] issuitably output. Namely, a signal level of each output port (P1, P2, P4,P5, P6) is suitably alternated between a low level [0] and a high level[1].

Each of the ports P_(int), P3, P7 and P8 is formed as an input port, towhich either a high level signal [1] or a low level signal [0] issuitably input. Namely, a signal level of each input port (P_(int), P3,P7, P8) is suitably alternated between a low level [0] and a high level[1].

The port P_(ad) is formed as an analog-to-digital (A/D) converter port.Namely, an analog signal is retrieved, as a digital data, by the CPU 123via the A/D converter port P_(ad).

The port P_(da) is formed as a digital-to-analog (D/A) converter port.Namely, a digital data is output, as an analog signal, from the CPU 123via the D/A converter port P_(da).

The port P_(a) is formed as an I/O port, and is connected to anelectrically erasable read-only memory (EEPROM) 124 storing variousdata, such as flash-light-emission correction data for the externalflash device 100.

The port P_(b) is formed as an I/O port, and connected to variousindicators, provided on the body 100 a of the external flash device 100,one of which is representatively indicated by reference 126. Theindicator 126 is used to announce whether an electrical charge of themain capacitor 109 is completed. For example, the indicator 126comprises a light-emitting diode (LED) which is lit when the electricalcharge of the main capacitor 109 is not completed.

The port P_(c) is formed as an I/O port, and is connected to connecterterminals 125 provided in the mount foot 150 (FIG. 1). When the clip-onmode is selected by manipulating the mode selection switch button 152,i.e when the external flash device is mounted on the camera body 10 a,the CPU 123 is connected to the system control circuit 40 through theconnector terminals 125.

The CPU 123 also has a power terminal V_(dd) connected to the battery106 through a regulator 122 and a Schottky diode 120, and is groundedthrough a ground terminal GND. When the power ON/OFF switch 154 a,connected to the input port P_(int), is turned ON by depressing thepower ON/OFF switch button 154 (FIG. 1), an ON-signal or high levelsignal [1] is input to the input port P_(int), thereby electricallyenergizing the CPU 123.

As shown in FIG. 4, the mode selection switch 152 is connected to theinput port P3. Whenever the mode selection switch 152 a is turned ON bydepressing the mode selection switch button 152 (FIG. 1), an ON-signalor high level signal [1] is input to the input port P3, therebyalternately switching the selection of the wireless mode and the clip-onmode. As already stated, in the situation as shown in FIG. 1, thewireless mode is selected.

The section G1 is formed as a step-up circuit including an oscillationcircuit having transistors 101 and 102, and a step-up transformer,generally indicated by reference 104, and the transformer 104 iselectrically powered by the battery 106 through the oscillation circuit,thereby developing a voltage high enough to electrically charge the maincapacitor 109.

In particular, when a high level signal [1] is output from the outputport P2, i.e. when a signal level of the output port P2 is changed froma low level [0] to a high level [1], a low level signal is input to thebase of the transistor 102 due to an existence of an invertor 102a (FIG.4), so that the transistor 102 is turned ON, thereby producing anemitter current in the transistor 102. Then, the transistor 101 isturned ON, due to the production of the emitter current in thetransistor 102, and thus a current flows through a primary winding P ofthe transformer 104, thereby developing a high voltage in a secondarywinding S of the transformer 104. The developed high voltage is appliedto the main capacitor 109 through a diode 105. When the transformer 104is magnetically saturated, the transistor 101 is temporarily turned OFF.In short, the turn-ON and the turn-OFF of the transistor 101 arerepeated such that the high voltages are successively applied to themain capacitor 109, thereby an electrical charge of the main capacitor109 is performed.

Note, the transformer 104 is provided with a subsidiary winding F, and avoltage, developed in the subsidiary winding F, is applied to theregulator 122 through a diode 121. Thus, it is possible to prevent achange in voltage of the power terminal V_(dd) of the CPU 123, even if adrop in the voltage of the battery 106 occurs during the charging of themain capacitor 109.

The section G2 is formed as a charge-voltage detector circuit fordetecting a charge voltage of the main capacitor 109. As is apparentfrom FIG. 3, the charge-voltage detector circuit G2, including resistors107 and 108, transistors 107 a and 108 a and so on, is constituted suchthat an electrical connection is established between the main capacitor109 and the resistors 107 and 108 while the charging of the maincapacitor 109 is performed due to the outputting of the high levelsignal from the output port P2.

Thus, the charge voltage of the main capacitor 109 is divided by theresistors 107 and 108 into two divided voltages, each of whichrepresents the charge voltage of the main capacitor 109. One of thedivided voltages is input to the A/D converter port P_(ad) of the CPU123. Namely, the divided voltage is suitably retrieved, as a digitalcharge voltage data representing the charge voltage of the maincapacitor 109, from the charge-voltage detector circuit G2, therebyproperly controlling the charging of the main capacitor 109. Forexample, the main capacitor 109 is charged until the charge voltagethereof becomes, for example, 330 volts.

The section G3 is formed as a flash-light-emission control circuit forcontrolling an electrical energization of the xenon lamp 115, i.e. aflash-light-emission of the xenon lamp 115. The flash-light-emissioncontrol circuit G3 includes a trigger transformer 111 having a primarywinding P and a secondary winding S, capacitors 112 and 113, a diode116, an insulated-gate bipolar transistor (IGBT) 117 and so on, andstarting and stopping of the flash-light-emission of the xenon lamp 115are controlled by turning the IGBT 117 ON and OFF.

When the charge voltage of the main capacitor 109 reaches 330 volts,i.e. the main capacitor 109 is completely charged, and when the IGBT 117is turned ON by an outputting of a high-level signal [1] from the outputport P1, an oscillation is caused between the capacitor 112 and theprimary winding P of the trigger transformer 111, thereby developing ahigh voltage in the secondary winding S of the trigger transformer 111,resulting in a flash-light-emission of the xenon lamp 115. At this time,a cathode potential of the diode 116 becomes zero, and thus both thevoltage of the capacitor 113 and the charge voltage of the maincapacitor 109 are applied to the xenon lamp 115. The voltage of thecapacitor 113 is equal to the charge voltage of the main capacitor 109,and thus the xenon lamp 115 is subjected to an application of twice asmuch voltage as the charge voltage of the main capacitor 109, wherebythe flash-light-emission of the xenon lamp 115 can be performed in astable condition. Of course, when the IGBT 117 is turned OFF by anoutputting of the low-level signal [0] from the output port P1, theflash-light-emission of the xenon lamp 115 is stopped.

The section G5 is formed as a light-receiver circuit associated with thelight receiver 155 for detecting a light-pulse signal (a reflected lightfrom the object A) emitted from the built-in flash device 16′ of thecamera 10 and an amount of flash-light-emission of the external flashdevice 100. Thus, the photo-transistor 138 of the light receiver 155forms a part of the light-receiver circuit G5.

The light-receiver circuit G5 includes an analog switch 130, a controlterminal C of which is connected to the output port P4. When a signallevel of the output port P4 is changed from a low level [0] to a highlevel [1], the analog switch 130 is turned ON, whereby thelight-receiver circuit G5 is electrically energized.

The light-receiver circuit G5 also includes analog switches 131, 132,133 and 134. Control terminals C of the analog switches 131 and 132 areconnected to the output ports P5 and P6, respectively, and each ofcontrol terminals C of the analog switches 133 and 134 is connected tothe output port P6 via an inverter 135.

When a signal level of the output port P5 is maintained at a low level[0], the analog switch 131 is in an OFF-state. Of course, when thesignal level of the output port P5 is changed from the low level [0] toa high level [1], the analog switch 131 is turned ON.

When a signal level of the output port P6 is maintained at a low level[0], the analog switch 132 is in an OFF-state, but the analog switches133 and 134 are in an ON-state, due to the existence of the inverter135. Of course, when the signal level of the output port P6 is changedfrom the low level [0] to a high level [1], the analog switch 132 isturned ON, and the analog switches 133 and 134 are turned OFF.

As is apparent from FIG. 4, the light-receiver circuit G5 is providedwith a differentiating circuit for detecting a light-pulse signalemitted from the built-in flash device 16′ of the camera 10. Namely, thedifferentiating circuit is formed by a capacitor 140, and resistors 141and 142, and is associated with a resistor 139 and a transistor 143. Thecollector of the photo-transistor 138 is connected to the resistor 139and the capacitor 140 via the analog switch 134. Thus, when the signallevel of the output port P6 is maintained at the low level [0], i.e.when the analog switch 134 is in the ON-state, an electrical connectionis established between the collector of the photo-transistor 138 and theresistor 139 and capacitor 140.

Accordingly, when the light-pulse signal, emitted from the built-inflash device 16′, is detected by the photo-transistor 138, a collectorcurrent is produced in the photo-transistor 138, and is fed to thedifferentiating circuit, resulting in an application of a voltage to thebase of the transistor 143. When the voltage exceeds a predeterminedthreshold, the transistor 143 is turned ON, and is then turned OFFimmediately. Namely, the ON-state of the transistor 143 remains for onlya very short time corresponding to an emission-time of the light-pulsesignal.

Note, a light-amount of the light-pulse signal, emitted from thebuilt-in flash device 16′, is previously set such that the voltagesufficiently exceeds the predetermined threshold, and thus, even thoughordinary external light is detected by the photo-transistor 138, thetransistor 143 cannot be turned ON.

While the ON-state of the transistor 143 remains for only the very shorttime corresponding to the emission-time of the light-pulse signal, asignal level of the input port P7, connected to the collector of thetransistor 143, is changed from a low level [0] to a high level [1].Namely, the CPU 123 detects the emission of the light-pulse signal fromthe built-in flash device 16′ by detecting the change of the signallevel of the input port P7.

Accordingly, as mentioned above, when the first light-pulse signal andthe second light-pulse signal are emitted from the built-in flash device16′, the CPU 123 detects the time interval, representing the second stopvalue, between the first light-pulse signal and the second light-pulsesignal. Also, when the emission of the second light-pulse signal isdetected by the CPU 123, the signal level of the output port P1 ischanged from the low level [0] to the high level [1], thereby turning ONthe IGBT 117, resulting in a flash-light emission of the xenon lamp 115.

The light-receiver circuit G5 is also provided with a set of capacitors136 and 137, arranged in parallel, in order to detect an amount of theflash-light-emission of the flash lamp 115 by the photo-transistor 138of the light receiver 155. The capacitor 136 has a capacitanceconsiderably larger than that of the capacitor 137. Namely, for example,in the first embodiment, a ratio of the capacitor 137 to the capacitor136 in capacitance is 1:31. The collector of the photo-transistor 138 isconnected to the capacitor 137 via the analog switch 132, and is furtherconnected to the capacitor 136 via both the analog switches 132 and 131.

When the analog switch 131 is in the OFF-state (P5=0), and when theanalog switch 132 is in the ON-state (P6=1), an electrical connection isestablished between the collector of the photo-transistor 138 and thecapacitor 137 exhibiting a small capacitance. When both the analogswitches 131 and 132 are in the ON-state (P5=1 and P6=1), an electricalconnection is established between the collector of the photo-transistor138 and both the capacitors 136 and 137 exhibiting a sum of thecapacitances of the capacitors 136 and 137. Namely, the latter isequivalent to a case where the collector of the photo-transistor 138 isconnected to a capacitor exhibiting a large capacitance which is 32times that of the capacitor 137.

When the flash-light-emission of the flash lamp 115 is detected as areflected light by the photo-transistor 138 of the light receiver 155, acollector current is produced in the photo-transistor 138. The producedcollector current is accumulated in either only the capacitor 137 orboth the capacitors 136 and 137, and thus a charge voltage is developedin either only the capacitor 137 or both the capacitors 136 and 137. Inparticular, when an amount of the flash-light-emission of the flash lamp115, to be detected, is small, the produced collector current isaccumulated in only the capacitor 137. On the other hand, when an amountof the flash-light-emission of the flash lamp 115, to be detected, islarge, the produced collector current is accumulated in both thecapacitors 136 and 137. Of course, in any event, a charge voltage isdeveloped in either only the capacitor 137 or both the capacitors 136and 137, and the amount of the flash-light-emission of the flash lamp115 is represented by the developed voltage.

Note, the electrical charges of the capacitor 137 are discharged byturning ON the analog switch 133, and the electrical charges of thecapacitor 136 are discharged by turning ON the analog switches 131 and133. Of course, while the charges of the capacitors 136 and 137 aredischarged, the analog switch 132 is in the OFF-state.

The light-receiver circuit G5 is further provided with a comparator 145associated with the capacitors 136 and 137, and the comparator 145 has afirst input terminal, indicated by a “minus symbol”, a second inputterminal, indicated by a “plus symbol”, and an output terminal. Thefirst input terminal of the comparator 145 is directly connected to thecapacitor 137, and is also connected to the capacitor 136 via the analogswitch 131. Namely, the charge voltage, developed in either only thecapacitor 137 or both the capacitors 136 and 137, is applied to thefirst input terminal of the comparator 145. The second input terminal ofthe comparator 145 is connected to the D/A converter port P_(da), andthe output terminal of the comparator 145 is connected to the input portP8.

The D/A converter port P_(da) outputs a reference voltage to the secondinput terminal of the comparator 145. The reference voltage is preparedby the CPU 123 on the basis of the time interval between the firstlight-pulse signal and the second light-pulse signal. As stated above,since the second stop value is represented by the time interval betweenthe first light-pulse signal and the second light-pulse signal, thereference voltage also represents the second stop value. Thus, thecharge voltage, developed in either only the capacitor 137 or both thecapacitors 136 and 137, is compared with the reference voltagerepresenting the second stop value.

When the charge voltage is less than the reference voltage, a low levelsignal [0] is output from the output terminal of the comparator 145 tothe input port P8. When the charge voltage reaches the referencevoltage, a high level signal [1] is output from the output terminal ofthe comparator 145 to the input port P8. When a signal level of theinput port P8 is changed from the low level [0] to the high level [1],the signal level of the output port P1 is changed from the high level[1] to the low level [0], thereby stopping the flash-light emission ofthe xenon lamp 115. Namely, an amount of the flash-light emission fromthe xenon lamp 115 corresponds to the second stop value.

FIG. 5 shows a timing chart in which the flash-light emission of theexternal flash device 100 is performed in the wireless mode. Of course,in this case, the external flash-ON mode is selected in the camera 10.

As stated above, in the external flash-ON mode (camera 10) and thewireless mode (external flash device 100), the light-pulse signal istwice emitted from the built-in flash device 16′. As shown in the timingchart of FIG. 5, the first light-pulse signal is emitted at a time ofT1, and then the second light-pulse signal is emitted at a time of T3. Atime interval between the first and second light-pulse signals,indicated by reference TA_(V), represents the aforesaid second stopvalue, and the second light-pulse signal serves as a flash-timing signalfor initiating the flash-light-emission of the external flash device100.

The first light-pulse signal, emitted from the built-in flash device16′, is reflected by the object A, and then is made incident on thelight receiver 155. The incident light-pulse signal is detected by thephoto-transistor 138, and thus a collector current is produced in thephoto-transistor 138, as indicated by reference S7, thereby turning ONthe transistor 143 (P6=0), resulting in a change of the signal level ofthe input port P7 from the low level [0], indicated by reference S13, tothe high level [1], indicated by reference S14. At this time, the CPU123 starts a measurement of the time interval TA_(V).

The emission of the first light-pulse signal from the built-in flashdevice 16′ ends at a time of T2. Namely, the emission of the firstlight-pulse signal continues over a short time interval between thetimes of T1 and T2, and thus the collector current is continuouslyproduced during the short time interval, thereby maintaining the signallevel of the input port P7 at the high level [1] therebetween.

When the emission of the first light-pulse signal is completed, theproduction of the collector current in the photo-transistor 138 expires.Namely, the collector current becomes zero in the photo-transistor 138,as indicated by reference S8, thereby turning OFF the transistor 143,resulting in a return of the signal level of the input port P7 to thelow level [0], as indicated by reference S15.

When the time of T3 has been reached, i.e. when the time interval TA_(V)has elapsed, the emission of the second light-pulse signal from thebuilt-in flash device 16′ starts. Similar to the emission of the firstlight-pulse signal, the emission of the second light-pulse signal isdetected by the photo-transistor 138, and thus a collector current isagain produced in the photo-transistor 138, as indicated reference S9,thereby tuning ON the transistor 143. Namely, the signal level of theinput port P7 is again changed from the low level [0], indicated byreference S15, to the high level [1], indicated by reference S16. Atthis time, the measurement of the time interval TA_(V) is completed bythe CPU 123.

After the detection of the emission of the second light-pulse signal,i.e. after the completion of the measurement of the time intervalTA_(V), a reference voltage is calculated by the CPU 123 on the basis ofthe measurement of the time interval TA_(V), and is then output from theD/A converter port P_(da) to the second input terminal of the comparator145, as indicated by reference S28.

Similar to the emission of the first light-pulse signal, the emission ofthe second light-pulse signal from the built-in flash device 16′ ends ata time of T4. Namely, the emission of the second light-pulse signalcontinues over a short time interval between the times of T3 and T4, andthus the collector current is continuously produced during the shorttime interval, thereby maintaining the signal level of the input port P7at the high level [1] therebetween.

When the emission of the second light-pulse signal is completed, theproduction of the collector current in the photo-transistor 138 expires.Namely, the collector current becomes zero in the photo-transistor 138,thereby turning OFF the transistor 143, resulting in a return of thesignal level of the input port P7 to the low level [0].

As soon as the signal level of the input port P7 returns to the lowlevel [0], the signal level of the output port P1 is changed from thelow level [0] to the high level [1], as indicated by reference S19,thereby turning ON the IGBT 117, resulting in a flash-light emission ofthe xenon lamp 115 of the external flash device 100, as indicated byreference S22.

Note, in the timing chart of FIG. 5, although the change of the signallevel of the output port P1 from the low level [0] to the high level [1]is caused at a time of T5 when a time period T_(d1) has elapsed from thetime of T4, the time period T_(d1) is as short as to be negligible. Thetime period T_(d1) is merely provided for the convenience ofillustration of the timing chart of FIG. 5. Namely, due to the provisionof the time period T_(d1), some pulse-waves can be averted from beingtoo close to each other on the timing chart. In short, the times of T4and T5 substantially coincide with each other.

By the change of the signal level of the output port P1 from the lowlevel [0] to the high level [1], the IGBT 117 is turned ON, whereby anflash-light emission of the xenon lamp 115 starts, as indicated byreference S22. The flash-light, emitted from the xenon lamp 115, isdetected as a reflected light by the photo-transistor 138 of the lightreceiver 155. Thus, a collector current is produced in thephoto-transistor 138, as indicated by reference S10.

On the other hand, when the change of the signal level of the outputport P1 from the low level [0] to the high level [1] is caused, thesignal level of the output port P6 is simultaneously changed from thelow level [0] to the high level [1], thereby turning ON the analogswitch 132. Also, if necessary, the signal level of the output port P5is changed from the low level [0] to the high level [1], thereby turningON the analog switch 131. Namely, the produced collector current isaccumulated in either only the capacitor 137 or both the capacitors 136and 137, thereby developing a charge voltage therein. The developedcharge voltage is gradually increased as indicated by reference S25, andis input to the first input terminal of the comparator 145.

Thus, in the comparator 145, the charge voltage, developed in eitheronly the capacitor 137 or both the capacitors 136 and 137, is comparedwith the reference voltage representing the second stop value. At a timeof T6 when the charge voltage (S25) reaches the reference voltage (S28),i.e. when a total amount of the flash-light emission from the xenon lamp115 reaches a proper amount of light represented by the second stopvalue, a signal level of the output terminal of the comparator 145 ischanged from a low level [0] to a high level [1], as indicated byreference S30. Then, when the high level signal [1] is input to theinput port P8, the signal level of the output port P1 is returned fromthe high level [1] to the low level [0], thereby turning OFF the IGBT117, resulting in stoppage of the flash-light emission from the xenonlamp 115. Thus, the object A is exposed with the proper amount of lightrepresented by the second stop value.

When the flash-light emission from the xenon lamp 115 is stopped, thesignal level of the output port P6 is changed from the high level [1] tothe low level [0], thereby turning ON the analog switch 133, and thusthe electrical charges are discharged from the capacitor 137. Of course,if both the capacitors 136 and 137 are charged during the flash-lightemission of the xenon lamp 115, the electrical charges are dischargedfrom the both capacitors 136 and 137.

During the detection of the flash-light emission from the xenon lamp115, the photo-transistor 138 also detects external light. Nevertheless,an amount of the external light is negligible, because the amount of thedetected external light is very small in comparison with the amount ofthe flash-light emission from the xenon lamp 115 to be detected.

FIG. 6 shows a flowchart of a main routine executed in the systemcontrol circuit 40 of the camera 10. Namely, the camera 10 operates inaccordance with the main routine. The main routine is constituted as aloop routine repeatedly executed at a predetermined time interval, andan execution of the main routine is started by loading the battery 70into the camera 10, regardless of the turn-ON and the turn-OFF of thepower ON/OFF switch 13 a.

At step S201, the system control circuit 40 is subjected toinitialization. Namely, the system control circuit 40 includes variouselements, such as CPU, RAM, input ports, output ports, registers and soon, and these elements are initialized.

At step S202, it is determined whether the film-rewinding switch 34 hasbeen turned ON. When the turn-ON of the switch 34 is confirmed, thecontrol proceeds to step S203, in which a forcible-rewinding routine isexecuted. Namely, the film, loaded in the camera 10, is forciblyrewound. It is detected by the film-feeding detector circuit 28 whetherthe rewinding of the film has been completed.

At step S202, if the film-rewinding switch 34 is in the OFF-state, thecontrol proceeds to step S204, in which it is determined whether achange of the back-cover switch 36 has occurred. When the back-coverswitch 36 has changed from an OFF-state to an ON-state, i.e. when it isreckoned that a loading of a film cartridge has been performed, thecontrol proceeds to step S205, in which a film-loading/processingroutine, involved in the loading of the film cartridge, is executed.

In executing the film-loading/processing routine, first, a film counter,contained in the system control circuit 40, is reset to “0” when theback-cover switch 36 is turned OFF (i.e. when the back-cover is opened).Note, a counting result of the film counter is displayed on the LCD 30.Also, the driver circuit 42 is operated, thereby driving thefilm-feeding motor M1 such that the film is drawn out of the filmcartridge by a predetermined length, and thus a first frame of the filmis positioned onto the photographing plane. Further, a DX code data,representing a sensitivity of the film, is read from the loaded filmcartridge by the DX code detector circuit 26.

At step S204, when a change has not occurred in the back-cover switch36, the control proceeds to step S206, in which it is determined whetherthe power ON/OFF switch 13 a is in an ON-state. When the power ON/OFFswitch 13 a is in an OFF-state, the control proceeds to step S207, inwhich it is determined whether the power ON/OFF switch 13 a has beenturned ON. When the power ON/OFF switch 13 a is in the OFF-state, thecontrol returns to step S202.

On the other hand, at step S207, when the turn-ON of the power ON/OFFswitch 13 a is confirmed, the control proceeds to step S208, in which apower-ON/processing routine, involved in the turn-ON of the power ON/OFFswitch 13 a, is executed. In executing the power-ON/processing routine,the lens barrel 23 is moved from the retracted position to the projectedposition, whereby the camera 10 is set in thephotographing-operation-enabling state. Thereafter, the control returnsto step S202.

At step S206, when the power ON/OFF switch 13 a is in the ON-state, thecontrol proceeds to step S209, in which it is determined whether thepower ON/OFF switch 13 a has been turned OFF. When the turn-OFF of thepower ON/OFF switch 13 a is confirmed, the control proceeds to stepS210, in which a power-OFF/processing routine, involved in the turn-OFFof the power ON/OFF switch 13 a, is executed. In executing thepower-OFF/processing routine, the lens barrel 23 is returned from theprojected position to the retracted position, whereby the camera 10 isset in the photographing-operation-disabling state. Further, variousfunctions of the camera 10 are initialized.

At step S209, when the turn-OFF of the power ON/OFF switch 13 a is notconfirmed, i.e. when the power ON/OFF switch 13 a is in the ON-state,the control proceeds to step S217, in which it is determined whether theflash-mode selection switch 11 a has been turned ON by a depression ofthe flash-mode selection switch button 11. When the turn-ON of theflash-mode selection switch 11 a is confirmed, the control proceeds tostep S218, in which a flash-mode setting routine is executed. In anexecution of the flash-mode setting routine, one of the automaticinternal flash mode, the internal flash-OFF mode, the internal flash-ONmode and the external flash-ON mode is selected and set. As mentionedabove, the selection of each individual flash mode is sequentially andcyclically switched in a given order by every turning ON of theflash-mode selection switch 11 a. After the selected flash mode is set,the control returns to step S202.

At step 217, when the turn-ON of the flash-mode selection switch 11 a isnot confirmed, the control proceeds to step S219, in which it isdetermined whether the photometry measurement switch 12 a has beenturned ON, i.e. whether the release switch button 12 has been partlydepressed. When the turn-ON of the photometry measurement switch 12 a isconfirmed, the control proceeds to step S220, in which a photographingoperation routine is executed. Of course, when the photometrymeasurement switch 12 a is turned ON, both the object-distancemeasurement circuit 21 and the photometry measurement circuit 22 areelectrically energized. Namely, an object-distance to the object A and aluminance of the object A are respectively measured by the circuits 21and 22, thereby producing an object-distance signal and a luminancesignal in the circuits 21 and 22.

Note, the photographing operation routine is explained in detailhereinafter with reference to FIGS. 7 and 8.

At step 217, when the turn-ON of the flash-mode selection switch 11 a isnot confirmed, the control proceeds to step S221, in which it isdetermined whether a flag F1 is “1” or “0”. The flag F1 indicateswhether an electrical charging of the main capacitor 16 b of thebuilt-in flash device 16′ is required. Namely, when the charge-requiringflag F1 is given a setting of “1”, the electrical charging of the maincapacitor 16 b is required, and, when the charge-requiring flag F1 isgiven a setting of “0”, the electrical charging of the main capacitor 16b is not required. Note, when the battery 70 is loaded into the camera10, the charge-requiring flag F1 is initialized to be “1” at step S201.

At step 221, if F1=1, the control proceeds to step S222, in which apre-charging routine is executed for performing the electrical chargingof the main capacitor 16 b, whereby the built-in flash device 16′ ismade available for a flash-light emission. On the other hand, if F1=0,the control returns to step S202.

Note, the pre-charging routine is explained in detail hereinafter withreference to FIG. 9.

After the power-ON/processing routine (S208) is executed or after aphotographing operation is performed with a flash-light emission of thebuilt-in flash device 16′, the charge-requiring flag F1 is made to be“1” for the electrical charging of the main capacitor 16 b. When theelectrical charging of the main capacitor 16 b is completed, thecharge-requiring flag F1 is made to be “0”.

FIGS. 7 and 8 show a flowchart of the photographing operation routineexecuted in step S220 of the main routine of FIG. 6.

At step S241, an object-distance measurement routine is executed,whereby the object-distance signal, representing the object-distance tothe object A, is retrieved as an object-distance data from theobject-distance measurement circuit 21 by the system control circuit 40.Then, at step S242, it is determined whether the retrievedobject-distance data falls in a focusing-permissible range in which afocusing of the object is available. Namely, it is determined whetherthe object A to be photographed is located within a focusing-allowabledistance range.

When the retrieved object-distance data falls in thefocusing-permissible range, the control proceeds to step S243, in whichthe green lamp 64 is lit, thereby announcing that a photographing ispossible. On the other hand, when the retrieved object-distance data isout of the focusing-permissible range, the control proceeds to stepS244, in which the green lamp 64 is blinked ON and OFF, therebyannouncing that a photographing is impossible.

In either event, at step S245, a photometry measurement routine isexecuted, whereby the luminance signal, which represents the luminanceof the object A, is retrieved as a luminance data from the photometrymeasurement circuit 22 by the system control circuit 40. Then, at stepS246, an automatic-exposure (AE) calculation routine is executed,whereby an exposure value is calculated on the basis of the retrievedluminance data. The calculated exposure value is utilized to determinewhether the built-in flash device 16′ should be allowed to emit aflash-light when the automatic internal flash mode is set.

Note, the AE calculation routine is explained in detail hereinafter withreference to FIG. 11.

At step S247, it is determined whether a flag F2 is “1” or “0”. The flagF2 indicates whether the built-in flash device 16′ should be allowed toemit a flash-light for illumination of the object A or for transmittanceof a light-pulse signal to the external flash device 100. Namely, whenthe flash-allowing flag F2 is given a setting of “1”, the built-in flashdevice 16′ should be allowed to emit the flash-light, and, when theflash-allowing flag F2 is given a setting of “0”, the built-in flashdevice 16′ should be not allowed to emit the flash-light.

At step S247, if F2=1, the control proceeds to step S248, in which anadditional-charging routine is executed for performing anadditional-electrical charging of the main capacitor 16b such that thebuilt-in flash device 16′ is allowed to emit a flash-light in aphotographing operation.

Note, the additional-charging routine is explained in detail hereinafterwith reference to FIG. 10. At a beginning of an execution of theadditional-charging routine, the red lamp 62 is blinked ON and OFF toannounce that the built-in flash device 16′ is in the course of theadditional-electric charging state. When the additional charging of themain capacitor 16 b is properly performed, the red lamp 62 is changedfrom the blinking-ON/OFF state to an ON-state. On the other hand, whenthe additional charging of the main capacitor 16 b is improperlyperformed, the red lamp 62 is changed from the blinking-ON/OFF state toan OFF-state.

At step S249, it is determined whether the additional charging of themain capacitor 16 b has been properly performed. When the performance ofthe additional charging of the main capacitor 16 b is proper, thecontrol proceeds to step S252. On the other hand, at step S247, if F2=0,i.e. if the built-in flash device 16′ should be not allowed to emit theflash-light, the control directly proceeds to step S252.

At step S252, it is determined whether the photometry measurement switch12 a is still in the ON-state. When the photometry measurement switch 12a is in the ON-state, the control proceeds to step S253, in which it isdetermined whether the release switch 12 b has been turned ON, i.e.whether the release switch button 12 has been fully depressed. If therelease switch 12 b is in the OFF-state, the control returns to stepS252.

Namely, the routine comprising steps S252 and S253 is repeated until therelease switch 12 b is turned ON. During the execution of the routinecomprising steps S252 and S253, if the photometry measurement switch 12a is turned OFF, i.e. if the partial depression of the release switchbutton 12 is emancipated, due to, for example, the photographingoperation concerned being canceled, the control proceeds from step S252to step S250, in which the green lamp 64 is turned OFF, with the redlamp 62 being also turned OFF, if lit. Then, the control returns to themain routine of FIG. 6.

Note, at step S249, if it is determined that the performance of theadditional charging of the main capacitor 16 b (S248) is improper, thecontrol proceeds from step S249 to step S250, in which the green lamp 64is turned OFF. Then, the control returns to the main routine of FIG. 6.

At step S253, when the turn-ON of the release switch 12 b is confirmed,the control proceeds to step S256, in which the green lamp 64 is turnedOFF, with the red lamp 62 being also turned OFF, if lit.

Then, at step S257, it is again determined whether the flash-allowingflag F2 is “1” or “0”. If F2=1, i.e. if the built-in flash device 16′should be allowed to emit the flash-light, the control proceeds fromstep S257 to step S260, in which a flashmatic (FM) calculation routineis executed. Then, the control proceeds to step S261.

Note, the FM calculation routine is explained in detail hereinafter withreference to FIG. 12.

When the photographing operation concerned should be performed byemitting the flash-light from the built-in flash device 16′, the firststop value, corresponding to a flash-light-emission aperture of theshutter, is calculated by the execution of the FM calculation routine.Note, as already stated, the flash-light-emission aperture is defined asan aperture of the shutter at which a flash-light is emitted from thebuilt-in flash device 16′ during an opening-action of the shutter.

On the other hand, when the photographing operation concerned isperformed by emitting the flash-light from the external flash device 100(FIG. 1), the second stop value, corresponding to a maximum aperture ofthe shutter during an opening-action of the shutter, is calculated bythe execution of the FM calculation routine, and a flash-light emissionof the external flash device 100 is initiated when an aperture of theshutter reaches the maximum aperture, as stated in detail hereinafter.

On the other hand, at step S257, if F2=0, i.e. if the built-in flashdevice 16′ should be not allowed to emit the flash-light, the controldirectly proceeds to step S261.

At step S261, a focusing routine is executed. In the execution of thefocusing routine, the focusing motor M2 is driven in accordance with theobject-distance data obtained in step S241, thereby actuating theautomatic focusing mechanism such that the photographing lens system 24is moved from the initial position until the object A is focused on thephotographing plane defined in the camera 10.

Then, at step S262, an exposure-controlling routine is executed. Inexecuting the exposure-controlling routine, the shutter motor M3 isdriven in accordance with the calculated results, obtained by theexecution of the AE calculation routine (S246), thereby actuating theshutter such that the object A is photographed with a given properexposure. Of course, if either the built-in flash device 16′ or theexternal flash device 100 is required to emit the flash-light, theflash-light emission is performed in accordance with the calculatedresults obtained by the execution of the FM calculation routine (S260).

Note, the exposure-controlling routine is explained in detailhereinafter with reference to FIG. 15.

After the execution of the exposure-controlling routine is completed,the control proceeds to step S263, in which a lens-system returningroutine is executed. In the execution of the lens-system returningroutine, the focusing motor M2 is driven such that the photographinglens system 24 is returned to the initial position.

At step S264, a film-feeding routine is executed. In the execution ofthe film-feeding routine, the film-feeding motor M1 is driven such thatthe film is wound on from the film cartridge by a length correspondingto one frame. Then, at step S265, it is determined whether the film hasended. If more film remains, the control returns to the main routine ofFIG. 6. At step S265, if the end of the film is confirmed, the controlproceeds to step S266, in which a film-rewinding routine is executed,whereby the film-feeding motor M1 is reversely driven until the film isrewound.

FIG. 9 shows a flowchart of the pre-charging routine executed in stepS222 of the main routine of FIG. 6. Note, the pre-charging routine isexecuted after the execution of the power-ON/processing routine (S208)or after the flash-light emission of the built-in flash device 16′, andthe main capacitor 16 b is fully charged by the execution of thepre-charging routine.

At step S281, a timer is started. For example, the timer is defined inthe system control circuit 40, and is constituted to count a time periodof 10 seconds. Then, at step S282, the step-up transformer circuit 16 ais operated under control of the system control circuit 40, whereby anelectrical charging of the main capacitor 16 b is started.

At step S283, a charge voltage data, representing a charge voltage ofthe main capacitor 16 b, is retrieved from the charge-voltage detectorcircuit 16 e. Then, at step S284, it is determined whether the chargevoltage of the main capacitor 16 b has reached a predetermined maximumvoltage, for example, 330 volts.

If the charge voltage of the main capacitor 16 b is less than 330 volts,the control proceeds to step S285, in which it is determined whether thetime period of 10 sec has been counted by the timer. When a counted timeof the timer has not reached 10 sec, the control proceeds to step S286,in which it is checked whether any one of the switch buttons (11, 12, 13and so on) has been manipulated. When no manipulation of any one of theswitch buttons is confirmed, the control returns to step S283. Namely,the routine comprising steps S283, S284, S285 and S286 is repeatedlyexecuted, thereby continuing the charging of the main capacitor 16 b.

At step S284, when it is confirmed that the charge voltage of the maincapacitor 16 b has reached 330 volts, the control proceeds step S287, inwhich the charge-requiring flag F1 is made to be “0”. Then, at stepS288, the charging of the main capacitor 16 b is stopped. Thereafter,the control returns to the main routine of FIG. 6.

At step S285, when a counted time of the timer has reached 10 secwithout the charge voltage of the main capacitor 16 b having reached 330volts at step S284, the control also proceeds step S287, in which thecharge-requiring flag F1 is made to be “0”. Then, at step S288, thecharging of the main capacitor 16 b is forcibly stopped.

Note, the timer is provided for protecting the main capacitor 16 b frombeing excessively charged. In particular, for example, when the chargevoltage of main capacitor 16 b cannot be properly detected due to thecharge-voltage detector circuit 16 e being damaged, the charging of themain capacitor 16 b cannot be stopped. Thus, the timer is necessary forthe main capacitor 16 b to be protected from being excessively charged.

At step S286, when it is confirmed that any one of the switch buttonshas been manipulated, the control proceeds to step S288, in which thecharging of the main capacitor 16 b is temporarily stopped. Then, thecontrol returns to the main routine of FIG. 6, and a processing,concerning the manipulated switch button, is executed. When theexecution of the processing concerned ends, the charging of the maincapacitor 16 b is resumed (F1=1).

FIG. 10 shows a flowchart of the additional charging routine executed instep S248 of the photographing operation routine of FIGS. 7 and 8.

At step S301, the red lamp 62 is blinked ON and OFF to announce that thebuilt-in flash device 16′ is in the course of the additional-electriccharging state. Then, at step S302, the timer, used in the pre-chargingroutine of FIG. 9, is started, to count a time period of 10 seconds.Then, at step S303, the step-up transformer circuit 16 a is operatedunder control of the system control circuit 40, whereby an electricalcharging of the main capacitor 16 b is started.

At step S304, a charge voltage data, representing a charge voltage ofthe main capacitor 16 b, is retrieved from the charge-voltage detectorcircuit 16 e. Then, at step S307, it is determined whether the chargevoltage of the main capacitor 16 b is at least 270 volts at which thexenon lamp 16 c can emit a flash-light.

At step S307, if the charge voltage of the main capacitor 16 b is equalto or more than 270 volts, the control proceeds to step S308, in whichthe charging of the capacitor 16 b is stopped. Then, at step S309, thered lamp 62 is changed from the blinking-ON/OFF state to an ON-state.That is, the red lamp 62 is continuously lit, thereby announcing thatthe charge voltage of the capacitor 16 b is high enough to emit aflash-light from the xenon lamp 16 c. Thereafter, the control returns tothe photographing operation routine of FIGS. 7 and 8.

At step S307, if the charge voltage of the main capacitor 16 b less than270 volts, the control proceeds to step S311, in which it is determinedwhether the time period of 10 sec has been counted by the timer. When acounted time of the timer has not reached 10 sec, the control proceedsto step S312, in which it is determined whether the photometrymeasurement switch 12 a is in the OFF-state, i.e. whether the partialdepression of the release switch button 12 is emancipated. When thephotometry measurement switch 12 a is still in the ON-state, the controlreturns to step S304. Namely, the routine comprising steps S304, S307,S311 and S312 is repeatedly executed, thereby continuing the charging ofthe main capacitor 16 b.

At step S307, when it is confirmed that the charge voltage of the maincapacitor 16 b has reached 270 volts, the control proceeds step S308, inwhich the charging of the main capacitor 16 b is stopped. Then, at stepS309, the red lamp 62 is continuously lit. Thereafter, the controlreturns to the photographing operation routine of FIGS. 7 and 8.

At step S311, when a counted time of the timer has reached 10 secwithout the charge voltage of the main capacitor 16 b having reached 270volts at step S307, the control skips to step S314, in which thecharging of the capacitor 16 b is stopped. Then, the red lamp 62 ischanged from the blinking-ON/OFF state to an OFF-state. That is, the redlamp 62 is turned OFF, thereby announcing that the main capacitor 16 bis not properly charged. Note, of course, the timer is provided for thesame reasons as the timer used in the pre-charging routine of FIG. 9.

During the execution of the routine comprising steps S304, S307, S311and S312, if the partial depression of the release switch button 12 isemancipated, thereby turning OFF the photometry measurement switch 12 a(S312), i.e if the photographing operation concerned is canceled, thecontrol proceeds from step S312 to step S313, in which thecharge-requiring flag F1 is made to be “1”. Then, at step S315, the redlamp 62 is turned OFF. Thereafter, the control returns to thephotographing operation routine of FIGS. 7 and 8. Note, in this case,due to F1=1, the pre-charging routine of FIG. 9 is executed forpreparing for a next photographing operation with a flash-emission ofthe built-in flash device 16′.

FIG. 11 shows a flowchart of the AE calculation routine executed in stepS246 of the photographing operation routine of FIGS. 7 and 8.

At step S331, an exposure value E_(v) is calculated on the basis of theAPEX (additive system of photographic exposure) system. Namely, thecalculation of the exposure value E_(V) is based on the followingequation:

E _(V) =B _(V) +S _(V)

Herein: B_(V) represents the luminance data retrieved from thephotometry measurement circuit 22 (S245); and S_(V) represents the DXcode data or sensitivity of the photographic film concerned detected bythe DX code detector circuit 26 (S205).

At step S332, it is determined whether the calculated exposure valueE_(V) is larger than a maximum exposure value E_(VMAX), corresponding toa maximum shutter speed (i.e. a shortest exposure time) which iscontrollable by the shutter of the camera 10. If E_(V)>E_(VMAX), thecontrol proceeds to step S333, in which the calculated exposure valueE_(V) is given a setting of the maximum exposure value E_(VMAX). Namely,whenever the calculated exposure value E_(V) is larger than the maximumexposure value E_(VMAX), the exposure value E_(V) is handled as themaximum exposure value E_(VMAX).

At step S334, it is determined whether the internal flash-OFF mode isselected. Of course, when the internal flash-OFF mode is selected, thebuilt-in flash device 16′ is not allowed to emit the flash-light. Thus,the control proceeds to step S335, in which the flash-allowing flag F2is made to be “0”, thereby prohibiting the flash-light emission of thebuilt-in flash device 16′.

Then, at step S336, it is determined whether the calculated exposurevalue E_(V) is smaller than a minimum exposure value E_(VMIN),corresponding to a minimum shutter speed (i.e. a longest exposure time)which is previously set in the shutter of the camera 10. IfE_(V)<E_(VMIN), the control proceeds to step S337, in which thecalculated exposure value E_(V) is given a setting of the minimumexposure value E_(VMIN). Thereafter, the control returns to thephotographing operation routine of FIGS. 7 and 8. Namely, whenever thecalculated exposure value E_(V) is smaller than the minimum exposurevalue E_(VMIN), the exposure value E_(V) is handled as the minimumexposure value E_(VMIN).

At step S336, if E_(V)≧E_(VMIN), the control immediately returns to thephotographing operation routine of FIGS. 7 and 8. Thus, the calculatedexposure value E_(V) is handled as it stands.

At step S334, when it is determined that the internal flash-OFF mode isnot selected, the control proceeds to step S338, in which it isdetermined whether either the internal flash-ON mode or the externalflash-ON mode is selected. Of course, when either the internal flash-ONmode or the external flash-ON mode is selected, the built-in flashdevice 16′ is allowed to emit the flash-light. Thus, the controlproceeds to step S339, in which the flash-allowing flag F2 is made to be“1”, thereby allowing the flash-light emission of the built-in flashdevice 16′.

Then, at step S340, it is determined whether the calculated exposurevalue E_(V) is smaller than a predetermined exposure value E_(VAUTO),corresponding to a hand-trembling-limit shutter speed at which ahand-trembling or camera-trembling is negligible upon photographing.Note, usually, the hand-trembling-limit shutter speed may be given asetting of {fraction (1/40)} sec. If E_(V)<E_(VAUTO), i.e. if a shutterspeed, corresponding to the calculated exposure value E_(V), is slowerthan the hand-trembling-limit shutter speed ({fraction (1/40)} sec), thecontrol proceeds to step S341, in which the calculated exposure valueE_(V) is given a setting of the predetermined exposure value E_(VAUTO).Thereafter, the control returns to the photographing operation routineof FIGS. 7 and 8. Namely, whenever the calculated exposure value E_(V)is smaller than the predetermined exposure value E_(VAUTO) the exposurevalue E_(V) is handled as the predetermined exposure value E_(VAUTO).

At step S340, if E_(V)≧E_(VAUTO), i.e. if the shutter speed,corresponding to the calculated exposure value E_(V), is equal to orfaster than the hand-trembling-limit shutter speed ({fraction (1/40)}sec), the control immediately returns to the photographing operationroutine of FIGS. 7 and 8. Thus, the calculated exposure value E_(V) ishandled as it stands.

At step S338, when it is determined that neither the internal flash-ONmode nor the external flash-ON mode is selected, i.e. when it isdetermined that the automatic internal flash mode is selected, thecontrol proceeds to step S342, in which the flash-allowing flag F2 ismade to be “0”, thereby prohibiting the flash-light emission of thebuilt-in flash device 16′.

Then, at step S343, it is determined whether the calculated exposurevalue E_(V) is smaller than the predetermined exposure value E_(VAUTO).If E_(V)<E_(VAUTO), i.e. if a shutter speed corresponding to thecalculated exposure value E_(V), is slower than the hand-trembling-limitshutter speed ({fraction (1/40)} sec), the control proceeds to stepS344, in which the flash-allowing flag F2 is made to be “1”, therebyallowing the flash-light emission of the built-in flash device 16′.Subsequently, at step S345, the calculated exposure value E_(V) is givena setting of the predetermined exposure value E_(VAUTO). Thereafter, thecontrol returns to the photographing operation routine of FIGS. 7 and 8.Namely, whenever the calculated exposure value E_(V) is smaller than thepredetermined exposure value E_(VAUTO), the exposure value E_(V) ishandled as the predetermined exposure value E_(VAUTO).

At step S343, if E_(V)≧E_(VAUTO), i.e. if the shutter expeed,corresponding to the calculated exposure value E_(V), is equal to orfaster than the hand-trembling-limit shutter speed ({fraction (1/40)}sec), the control immediately returns to the photographing operationroutine of FIGS. 7 and 8. Thus, the calculated exposure value E_(V) ishandled as it stands.

FIG. 12 shows a flowchart of the FM calculation routine executed in stepS260 of the photographing operation routine of FIGS. 7 and 8.

At step S361, a minimum stop value A_(VPEAK) is calculated on the basisof the exposure value E_(V) obtained by the execution of the EVcalculation routine of FIG. 11. The minimum stop value A_(VPEAK)corresponds to a maximum aperture of the shutter of the camera 10 duringan opening-action of the shutter. Namely, in the execution of theexposure-controlling routine (S262), the shutter of the camera 10 isopened until an aperture of the shutter reaches the maximum aperturecorresponding to the minimum stop value A_(VPEAK), and then the shutterof the camera 10 is immediately closed.

Referring to a graph of FIG. 13, a variation in the aperture of theshutter is conceptually shown by way of example, and, referring to atable of FIG. 14, a relationship between an exposure value E_(V) and acorresponding minimum stop value A_(VPEAK) is shown by way of example.In the table of FIG. 14, for example, when an exposure value E_(V) is“11”, the exposure value of “11” corresponds to a minimum stop valueA_(PEAK) of “3.5”, corresponding to a maximum aperture of the shutterwhich is determined on the basis of the exposure value of “11”. In thiscase, the aperture of the shutter is varied along an exposure waveprofile ΔAHI, an apex (H) of which corresponds to the minimum stop valueA_(VPEAK) of “3.5”.

Also, a duration of shutter-open time TE_(V) of the shutter is definedas a time which is counted from a time of point (A), at which theshutter begins to open, to a point of time at which the aperture of theshutter reaches a minimum stop value A_(VPEAK) (B, D, F, H, J). Thus, inthe aforesaid example, the shutter-open time duration TE_(V) isrepresented by “T13”.

In the first embodiment, the table of FIG. 14 (except for the exposurewave profile column) is formed as a two-dimensional map, and isincorporated in the system control circuit 40. Thus, at step S361, thecalculation of the minimum stop value A_(VPEAK) based on the exposurevalue E_(V) is immediately ascertained using the two-dimensional map.

At step S362, it is determined whether the external flash-ON mode isselected. When the external flash-ON mode is not selected, i.e. when theobject A is illuminated by the flash-light emission of the built-inflash device 16′, the control proceeds to step S366, in which a signal,representing a charge voltage of the main capacitor 16 b, is retrievedas a charge voltage data from the charge-voltage detector circuit 16 e,and a guide number G_(no) is calculated on the basis of the retrievedcharge voltage data.

As is well known, the guide number G_(no) represents an amount of theflash-light emitted from the xenon lamp 16 c when it is electricallyenergized with an electrical discharge of the charged main capacitor 16b, and the retrieved charge voltage data represents an amount of theelectrical charges of the main capacitor 16 b. Thus, it is possible tocalculate the guide number G_(no) on the basis of the retrieved chargevoltage data.

In the first embodiment, a relationship between a guide number G_(no)and a charge voltage data of the main capacitor 16 b is also formed as atwo-dimensional map, and is incorporated in the system control circuit40. Thus, at step S366, the calculation of the guide number G_(no) basedon the retrieved charge voltage data is immediately ascertained usingthe two-dimensional map.

At step S367, a first stop aperture A_(V1), corresponding to aflash-light-emission aperture, is calculated. Note, as explainedhereinbefore, the flash-light-emission aperture is defined as anaperture of the shutter at which a flash-light emission of the built-inflash device 16′ should be started during an opening-action of theshutter.

In particular, first, an f-number F_(no) is calculated from the guidenumber G_(no) as follows:

F _(no) =G _(no) /D

Herein: D is the object-distance data obtained in step S241 of thephotographing operation routine of FIGS. 7 and 8.

Then, the first stop aperture A_(V1) is calculated as follows:

A _(V1)=2×log(F _(no))/log 2+(S _(v)−5)

Herein: S_(V) represents the DX code data or sensitivity of thephotographic film concerned detected by the DX code detector circuit 26(S205), as already stated hereinbefore.

At step S368, it is determined whether the calculated first stop valueA_(V1) is less than the minimum stop value A_(VPEAK) corresponding tothe maximum aperture of the shutter of the camera 10. IfA_(V1)<A_(VPEAK), the control proceeds to step S369, in which thecalculated first stop value A_(V1) is given a setting of the minimumstop value A_(PEAK). Namely, the calculated first stop value A_(V1) ishandled as the minimum stop value A_(VPEAK).

At step S368, if A_(V1)≧A_(VPEAK), the control proceeds to step S370, inwhich it is determined whether the calculated first stop value A_(V1) islarger than a maximum limit stop value A_(VMAX) corresponding to aminimum aperture which is controllable by the shutter of the camera 10.If A_(V1)>A_(VMAX), the control proceeds to step S371, in which thecalculated first stop value A_(V1) is given a setting of the maximumlimit stop value A_(MAX). Namely, the calculated first stop value A_(V1)is handled as the maximum limit stop value A_(VMAX).

At step S370, if A_(V1)≦A_(VMAX), the control returns to thephotographing operation routine of FIGS. 7 and 8. In this case, ofcourse, the calculated first stop value A_(V1) is handled as it stands.

At step S362, when the external flash-ON mode is selected, i.e. when theobject A is illuminated by the flash-light emission of the externalflash device 100, the control proceeds to step S363, in which a secondstop value A_(V2), at which the flash-light emission of the externalflash device 100 should be started, is given a setting of the minimumstop value A_(VPEAk). Namely, the flash-light emission of the externalflash device 100 is started when the aperture of the shutter reaches themaximum aperture corresponding to the minimum stop value A_(VPEAK).

Then, at step S364, an exposure factor A_(V)E to be transmitted to theexternal flash device 100 is calculated by subtracting a filmsensitivity correction value (S_(V)−5) from the second stop value A_(V2)as follows:

A _(V) E←A _(V2)−(S _(V)−5)

Herein: of course, S_(V) represents the DX code data or sensitivity ofthe photographic film concerned detected by the DX code detector circuit26 (S205), and the film sensitivity correction value (S_(V)−5) isdetermined on the basis of “ISO 100”. Note, the exposure factor A_(V)Eis a factor corresponding to the stop value of the shutter during theopening-action of the shutter.

Thereafter, the control returns to the photographing operation routineof FIGS. 7 and 8.

Note, as stated in detail hereinafter, when a light-flash is emittedfrom the external flash device 100, an amount of the flash-lightemission is determined in accordance with the exposure factor A_(V)E.Also, note, in the first embodiment, it is possible to omit a setting ofa film-sensitivity to be given to the external flash device 100, becausethe exposure factor A_(V)E is obtained by processing the second stopvalue A_(V2) with the correction value (S_(V)−5).

FIGS. 15 and 16 show a flowchart of the exposure-controlling routineexecuted in step S262 of the photographing operation routine of FIGS. 7and 8.

At step S401, a duration of shutter-open time TE_(V) of the shutter iscalculated on the basis of the exposure value E_(V) obtained by theexecution of the AE calculation routine of FIG. 11. Namely, theshutter-open time duration TE_(V) is immediately determined from theaforesaid two-dimensional map based on the table of FIG. 14.

At step S402, it is determined whether the flash-allowing flag F2 is “1”or “0”. If F2=0, i.e. if the photographing operation is executed withoutemitting the flash-light from either the built-in flash device 16′ orthe external flash device 100, the control proceeds to step S408, inwhich the shutter motor M3 is driven so that the shutter of the camera10 is opened.

Then, at step S409, it is monitored whether the shutter switch 32 hasbeen turned ON. When it is confirmed that the shutter switch 32 isturned ON, i.e. when an opening-action of the shutter has just started,the control proceeds to step S410, in which a first timer TM1 isstarted. Note, a starting point of the shutter-opening-action isindicated by reference “A” in the graph of FIG. 13.

For example, the first timer TM1 is defined in the system controlcircuit 40, and is constituted to count a duration of shutter-open timeof the shutter. Namely, at step S410, the shutter-open duration time TEvobtained in step S401 is set in the first timer TM1, and a time-countingis started by the first timer TM1.

At step S411, it is again determined whether the flash-allowing flag F2is “1” or “0”. If F2=0, the control proceeds to step S414, in which itis monitored whether the shutter-open duration time TE_(V) has beencounted by the first timer TM1. When it is confirmed that theshutter-open duration time TE_(V) has been counted by the first timerTM1, i.e. when it is confirmed that the aperture of the shutter hasreached the maximum aperture corresponding to the minimum stop valueA_(VPEAK) concerned, the control proceeds to step S415, in which theshutter motor M3 is reversely driven so that a closing-action of theshutter is started.

At step S416, it is monitored whether the shutter switch 32 has beenturned OFF. When it is confirmed that the shutter switch 32 has beenturned OFF, i.e. when the shutter has returned to the starting point ofthe shutter-opening-action, as indicated by reference “A” in the graphof FIG. 14, the control proceeds to step S417, in which thereverse-driving of the shutter motor M3 is continued for a short timeperiod of, for example, 50 ms, whereby the blades of shutter can becompletely returned to the initial position.

Then, at step S418, the shutter motor M3 is stopped, and thus theexposure-controlling routine ends without emitting the flash-light fromthe built-in flash device 16′ nor the external flash device 100 (F2=0).Thereafter, the control returns to the photographing operation routineof FIGS. 7 and 8.

At step S402, if F2=1, i.e. if the photographing operation is executedwith emitting the flash-light from either the built-in flash device 16′or the external flash device 100, the control proceeds to step S403, inwhich either a first trigger time T_(trg1) or a second trigger timeT_(trg2) is calculated. Note, the first trigger time T_(trg1) is definedas a time at which a flash-light should be emitted from the built-inflash device 16′, and the second trigger time T_(trg2) is defined as atime at which a flash-light should be emitted from the external flashdevice 100 should be started. The first and second trigger timesT_(trg1) and T_(trg2) are calculated on the basis of the first andsecond stop values A_(V1) and A_(V2), respectively.

When the first stop value A_(V1) is obtained by the execution of the FMcalculation routine of FIG. 13, i.e. when the external flash-ON mode isnot selected (S362), the trigger time T_(trg1) is calculated as a periodof time between the time at which the opening-action of the shutter isstarted and the time at which the aperture of the shutter reaches theflash-light-emission aperture corresponding to the first stop valueA_(V1). Referring to a graph of FIG. 17, a relationship between a firststop value A_(V1) and a trigger time T_(trg1) is shown. For example,when the first stop value A_(V1) is “4”, the trigger time T_(trg1) isgiven a setting of “T23”.

Note, in the first embodiment, the relationship as shown in the graph ofFIG. 17 is formed as a two-dimensional map, and is incorporated in thesystem control circuit 40, whereby the calculation of the trigger timeT_(trg1) can be immediately ascertained using the two-dimensional map.

On the other hand, when the second stop value A_(V2) is obtained by theexecution of the FM calculation routine of FIG. 12, i.e. when theexternal flash-ON mode is selected (S362), the trigger time T_(trg2) iscalculated as the shutter-open duration time TE_(V). Namely, thecalculation of the trigger time T_(trg2) can be immediately ascertainedusing the aforesaid two-dimensional map based on the table of FIG. 14.Note, as stated above, the flash-light emission of the external flashdevice is started when the aperture of the shutter has reached themaximum aperture corresponding to the minimum stop value A_(VPEAK).

At step S404, it is determined whether the external flash-ON mode isselected. When it is confirmed that the external flash-ON mode is notselected, the control proceeds to step S407, in which a variable or timeT_(a1) is made to be “T_(trg1)”, and a variable or time T_(b1) is madeto be, for example, “10 ms”.

On the other hand, at step S404, when it is confirmed that the externalflash-ON mode is selected, the control proceeds to step S405, in which atime interval data TA_(V) is calculated on the basis of the exposurefactor A_(V)E obtained in step S364 of the FM calculation routine ofFIG. 12.

As is apparent from the foregoing, when the external flash-ON mode isselected, a flash-light is twice emitted as a light-pulse signal fromthe built-in flash device 16′ such that the exposure factor A_(V)E isrepresented by the time interval TA_(V) between the twice-emittedlight-pulse signals: the first light-pulse signal and the secondlight-pulse signal, and such that the second light-pulse signal servesas a flash-timing signal for initiating the flash-light-emission of theexternal flash device 100.

Referring to a table of FIG. 18, a relationship between an exposurefactor A_(V)E and a time interval TA_(V) is shown. For example, when theexposure factor A_(V)E is “2.8”, the time interval TA_(V) is given asetting of “1.2 ms”. Note, the relationship between the exposure factorA_(V)E and the time interval TA_(V) is formed as a two-dimensional map,and is incorporated in the system control circuit 40, whereby thecalculation of the time interval TA_(V) can be immediately ascertainedby referring to the two-dimensional map.

At step S406, a variable or time T_(a2) is made to be“(T_(trg2)−TA_(V))”, and a variable or time T_(b2) is made to be“TA_(V)”.

After the setting of either the times T_(a1) and T_(b1) or the timesT_(a2) and T_(b2) (S407 or S406), the routine comprising steps S408,S409 and S410 is executed in the same manner as mentioned above.

Then, at step S411, it is determined whether the flash-allowing flag F2is “1” or “0”. At this stage, since F2=1, the control proceeds from stepS411 to step S412, in which a second timer TM2 is given a setting ofeither the time T_(a1) or the time T_(a2), and is then started. Ofcourse, when the external flash-ON mode is not selected, the time T_(a1)is set in the second timer TM2, and, when the external flash-ON mode isselected, the time T_(a2) is set in the second timer TM2.

Note, similarly to the first timer TM1, the second timer TM2 is definedin the system control circuit 40, and is constituted to count the settime (T_(a1) or T_(a2)). Also, note, when the set time (T_(a1) orT_(a2)) has been counted by the second timer TM2, an interruption signalis output from the second timer TM2 to the CPU of the system controlcircuit 40.

At step S413, the interruption signal to be output from the second timerTM2 is enabled to execute a timer-interruption routine as shown in FIG.19. Thereafter, the routine comprising steps S414 to S418 is executed inthe same manner as mentioned above.

FIG. 19 shows a flowchart of the timer-interruption routine, which isexecuted by outputting an interruption signal from the second timer TM2.

At step S431, it is determined whether the external flash-ON mode isselected. When it is confirmed that the external flash-ON mode is notselected, i.e when the second timer TM2 is given the setting of the timeT_(a1) (T_(trg1)), the control proceeds to step S432, in which it isdetermined whether the outputting of the interruption signal from thesecond timer TM2 is a first time. When the outputting of theinterruption signal is the first time, the control proceeds to stepS433, in which the second timer TM2 is given a setting of the timeT_(b1) (10 ms), and is again started.

Then, at step S434, a trigger signal is output from the system controlcircuit 40 to the IGBT of the flash-light-mission control circuit 16 d,thereby turning ON the IGBT, resulting in energization of the xenon lamp16 c by discharging the electrical charges from the main capacitor 16 b.Thus, a flash-light emission of the built-in flash device 16′ isstarted. Thereafter, the control returns to the exposure-controllingroutine of FIGS. 15 and 16.

When the set time T_(b1) (10 ms) has been counted by the second timerTM2, an interruption signal is output as a second time signal fromthe-second timer TM2 to the CPU of the system control circuit 40,whereby the timer-interruption routine is again executed. Thus, in thesecond time execution of the timer-interruption routine, the controlproceeds from step S432 to step S435, in which an interruption signal tobe output from the second timer TM2 is disabled.

Then, at step S436, the outputting of the trigger signal from the systemcontrol circuit 40 to the IGBT of the flash-light-emission controlcircuit 16 d is stopped, thereby turning OFF the IGBT, resulting inde-energization of the xenon lamp 16 c. Thus, the flash-light emissionof the built-in flash device 16′ is stopped.

Note, the time T_(b1) (10 ms) is selected as a time long enough tocomplete the discharge of the electrical charges from the fully-chargedmain capacitor 16 b. Also, note, since a total time of the times T_(a1)and T_(b1) is shorter than the shutter-open duration time TE_(V), theexecution of the timer-interruption routine can be twice repeated untilthe shutter-open duration time TE_(V) has been counted by the firsttimer TM1 (S414).

At step S431, when it is confirmed that the external flash-ON mode isselected, i.e when the second timer TM2 is given the setting of the timeT_(a2) (T_(trg2)−TA_(V)), the control proceeds to step S438, in which itis determined whether the outputting of the interruption signal from thesecond timer TM2 is a first time. When the outputting of theinterruption signal is the first time, the control proceeds to stepS439, in which the second timer TM2 is given a setting of the timeT_(b2) (TA_(V)), and is again started.

At step S441, a trigger signal is output from the system control circuit40 to the IGBT of the flash-light-emission control circuit 16 d, therebyturning ON the IGBT, resulting in energization of the xenon lamp 16 c bydischarging the electrical charges from the main capacitor 16 b. Thus, aflash-light emission of the built-in flash device 16′ is started.

Then, at step S442, it is monitored whether a very short time of, forexample, 100 μs has elapsed. When it is confirmed that the very shorttime of 100 μs has elapsed, the control proceeds to step S443, in whichthe outputting of the trigger signal from the system control circuit 40to the IGBT of the flash-light-emission control circuit 16 d is stopped,thereby turning OFF the IGBT, resulting in de-energization of the xenonlamp 16 c. Thus, the flash-light emission of the built-in flash device16′ is stopped.

In short, the flash-light emission of the built-in flash device 16′ iscontinued over the very short time of 100 μs, and is thus received as afirst light-pulse signal by the external flash device 100. Thereafter,the control returns to the exposure-controlling routine of FIGS. 15 and16.

When the set time T_(b2) (TA_(V)) has been counted by the second timerTM2, an interruption signal is output as a second time signal from thesecond timer TM2 to the CPU of the system control circuit 40, wherebythe timer-interruption routine is again executed. Thus, in the secondtime execution of the timer-interruption routine, the control proceedsfrom step S438 to step S440, in which an interruption signal to beoutput from the second timer TM2 is disabled.

At step S441, a trigger signal is again output from the system controlcircuit 40 to the IGBT of the flash-light-emission control circuit 16 d,thereby turning ON the IGBT, resulting in energization of the xenon lamp16 c by discharging the electrical charges from the main capacitor 16 b.Thus, a flash-light emission of the built-in flash device 16′ is againstarted.

Then, at step S442, it is monitored whether a very short time of, forexample, 100 μs has elapsed. When it is confirmed that the very shorttime of 100 μs has elapsed, the control proceeds to step S443, in whichthe outputting of the trigger signal from the system control circuit 40to the IGBT of the flash-light-emission control circuit 16 d is stopped,thereby turning OFF the IGBT, resulting in de-energization of the xenonlamp 16 c. Thus, the flash-light emission of the built-in flash device16′ is stopped.

In short, the second flash-light emission of the built-in flash device16′ is also continued over the very short time of 100 μs, and is thusreceived as a second light-pulse signal by the external flash device100. Thereafter, the control returns to the exposure-controlling routineof FIGS. 15 and 16.

FIGS. 20 and 21 show a flowchart of a main routine executed in the CPU123 of the external flash device 100. Note, the main routine is executedwhen the battery 106 is loaded or when the power ON/OFF switch 154 a isturned ON by depressing the power ON/OFF switch button 154.

At step S101, the CPU 123 is initialized. For example, in each of theoutput ports P1, P3, P4, P5, P6 and P_(da), an output signal level isset to be a low level [0]. Also, each of other input ports P3, P7, P8,P_(int), P_(a), P_(b), P_(c), P_(ad) and so on is initialized so that apredetermined function can be properly performed.

At step S102, the various data, including flash-light-emissioncorrection data, are read from the EEPROM 124 via the port P_(a), andthe read data are stored in a memory contained in the CPU 123. Then, atstep S103, a charge-indicating flag F_(charge) is reset to be “0”. Note,if F_(charge)=0, it indicates that an electrical charge of the maincapacitor 109 is unfinished, and, if F_(charge)=1, it indicates that anelectrical charge of the main capacitor 109 is finished.

At step S104, a 125 ms-timer-interruption is enabled. In particular, theCPU 123 is provided with a timer which outputs an interruption signal ata regular time-interval of 125 ms, and a 125 ms-timer-interruptionroutine, as shown in FIG. 22, is executed by every outputting of theinterruption signal from the timer, whereby the main capacitor 109 iselectrically charged to a predetermined charge voltage, as stated indetail hereinafter. In short, the execution of the 125ms-timer-interruption routine is allowed only while the 125ms-timer-interruption is enabled.

At step S105, it is determined whether the flag F_(charge) is “1” or“0”. If F_(charge)=1, i.e. if the charge of the main capacitor 109 isfinished, the control proceeds to step S106, in which it is determinedwhether the wireless mode is selected by manipulating the mode selectionswitch button 152.

When the wireless mode is selected, the control proceeds to step S107,in which the signal level of the output port P4 is caused to be high[1], thereby turning ON the analog switch 130, resulting in energizationof the light-receiver circuit G5. Also, at step S107, the signal levelof the output port P5 is caused to be high [1], thereby turning ON theanalog switch 131. Further, the signal level of the output port P6 iscaused to be low [0], thereby turning ON the analog switches 133 and134. At this time, of course, the analog switch 132 is in the OFF-state.Thus, the external flash device 100 makes preparations for receiving alight-pulse signal from the built-in flash device 16′ of the camera 10.

At step S108, a P7-interruption is enabled. Namely, when the signallevel of the input port P7 is changed from the low level [0] to the highlevel [1], the high level signal [1] is allowed to be retrieved as aninterruption signal by the CPU 123, thereby executing a P7-interruptionroutine as shown in FIGS. 23 and 24. Note, in the execution of theP7-interruption routine, a flash-light emission of the external flashdevice 100 is performed in accordance with an emission of aforesaidfirst and second light-pulse signals from the built-in flash device 16′,as stated in detail hereinafter.

At step S112, it is determined whether the power ON/OFF switch 154 a isin the OFF-state. When the power ON/OFF switch 154 a is in the ON-state,the control returns to step S105.

On the other hand, at step S105, when F_(charge)=0, i.e. when thecharging of the main capacitor 109 is unfinished, the control proceedsto step S109, in which the P7-interruption is disabled, due to thecharging of the main capacitor 109 being unfinished. Also, at step S106,when the wireless mode is not selected, i.e. when the clip-on mode isselected, the control proceeds to step S109, in which theP7-interruption is disabled, whereby the flash-light emission of theexternal flash device 100 is prohibited in the wireless mode. In short,when the flag F_(charge) is “0” or when the clip-on mode is selected,the P7-interruption routine cannot be executed.

At step S110, the signal level of the output port P4 is caused to be low[0], thereby turning OFF the analog switch 130, resulting inde-energization of the light-receiver circuit G5. Also, at step S110,the signal level of the output port P5 is caused to be low [0], and thesignal level of the output port P6 is caused to be low [0], resulting ina standstill of the photo-transistor 138. Further, at step S110, theinput level of the port P_(ad) is caused to be low [0], therebydisabling a detection of a charge voltage of the main capacitor 109.Thus, the external flash device 100 can not operate in the wirelessmode.

At step S111, a clip-on mode operation routine is executed so that theCPU 123 can be communicated with the system control circuit 40 of thecamera 10 in a well-known manner, whereby a flash-light emission of theexternal flash device 100 is controlled by the system control circuit 40of the camera 10.

Then, the control proceeds to step S112, in which it is determinedwhether the power ON/OFF switch 154 a is in the OFF-state. When thepower ON/OFF switch 154 a is in the ON-state, the control returns tostep S105.

As is apparent from the foregoing, as long as the power ON/OFF switch154 a is in the ON-state, the routine comprising steps S105 to S112 isrepeatedly executed.

At step S112, when it is confirmed that the power ON/OFF switch is inthe OFF-state, the control proceeds to step S113, in which allinterruption-processings are prohibited in the CPU 123. At step S114,the output ports P1, P3, P4, P5, P6 and P_(da) are initialized. Then, atstep S115, the input port P_(int) is enabled so as to receive anON-signal from the power ON/OFF switch 145 a. Thereafter, at step S116,the CPU 123 is put in a sleep mode in which a power consumption isapproximately zero. Thus, the main routine cannot be executed until thepower ON/OFF switch 154 a is turned ON.

FIG. 22 shows a flowchart of the 125 ms-interruption routine. As statedabove, when the 125 ms-timer-interruption is enabled at step S104 of themain routine of FIGS. 20 and 21, the 125 ms-interruption routine isexecuted at the regular time-interval of 125 ms.

At step S120, the 125 ms-timer-interruption is disabled, due to the CPU123 being in the course of the execution of the 125 ms-interruptionroutine.

At step S121, the signal level of the output port P2 is caused to behigh [1], thereby starting an electrical charge of the main capacitor109. Then, at step S122, a digital charge voltage data CV, representinga charge voltage of the main capacitor 109, is retrieved from thecharge-voltage detector circuit G2 via the port P_(ad). At step S123, itis determined whether the charge voltage data CV is larger than apredetermined maximum voltage data V_(max) (e.g. 330 volts). Note, themaximum voltage data V_(max) is stored in the EEPROM 124, and is readfrom the EEPROM 124 in step S102 of the main routine of FIGS. 20 and 21.

At step S123, if CV≦V_(max), the control proceeds to step S125, in whichit is determined whether the charge voltage data CV is larger than aminimum voltage data V_(min), which is necessary to electricallyenergize the xenon lamp 115. Note, the minimum voltage data V_(min) isalso stored in the EEPROM 124, and is read from the EEPROM 124 in stepS102 of the main routine of FIGS. 20 and 21.

At step S125, if CV≦V_(min), the control proceeds to step S126, in whichthe charge-indicating flag F_(charge) is made to be “0”. Then, at stepS127, the indicator or LED 126 is lit to announce that the electricalcharge of the main capacitor 109 is unfinished. Thereafter, at stepS130, the 125 ms-timer-interruption is enabled, and the control returnsto the main routine of FIGS. 20 and 21.

At step S123, if CV>V_(max), i.e. if the main capacitor 109 issufficiently charged, the control proceeds to step S124, in which thesignal level of the output port P2 is caused to be low [0], therebystopping the electrical charge of the main capacitor 109. Then, at stepS128, the flag F_(charge) is made to be “1”. Subsequently, at step S129,the indicator or LED 126 is turned OFF to announce that a flash-lightemission of the external flash device 100 is allowable.

At step S125, if CV>V_(min), i.e. if the main capacitor 109 is chargedto a level which is necessary to electrically energize the xenon lamp115, the control proceeds to step 128, in which the flag F_(charge) ismade to be “1”. Then, at step S129, the indicator or LED 126 is turnedOFF to announce that a flash-light emission of the external flash device100 is allowable.

Accordingly, when the power ON/OFF switch 154 a is in the ON-state, themain capacitor 109 can be charged to the maximum voltage level (e.g. 330volts).

FIGS. 23 and 24 show a flowchart of the P7-interruption routine. Asmentioned above, the P7-interruption routine is executed when theP7-interruption is enabled at step S108 of the main routine of FIGS. 21and 22, and when the signal level of the input port P7 is changed fromthe low level [0] to the high level [1]. Namely, the execution of theP7-interruption routine is started when the first light-pulse signal,emitted from the built-in flash device 16′ of the camera 10, is detectedby the light receiving circuit G5. Thus, the time, at which the signallevel of the input port P7 is changed from the low level [0] to the highlevel [1], corresponds to the time of T1 shown in the timing chart ofFIG. 5.

At step S140, all interruption-processings are prohibited in the CPU123. Then, at step S141, a timer is started. Note, the timer may bedefined in the CPU 123, and is utilized to count a time between thefirst and second light-pulse signals emitted from the built-in flashdevice 16′.

At step S142, it is monitored whether the signal level of the input portP7 is changed from the high level [1] to the low level [0]. When thechange of the signal level of input port P7 from the high level [1] tothe low level [0] is confirmed (T2 in FIG. 5), the control proceeds tostep S143, in which it is determined whether the signal level of theinput port P7 is again changed from the low level [0] to the high level[1], i.e. it is determined whether the second light-pulse signal,emitted from the built-in flash device 16′ of the camera 10, is detectedby the light receiving circuit G5.

At step 143, when the change of the signal level of input port P7 fromthe low level [0] to the high level [1] is not confirmed, the controlproceeds to step S145, in which it is determined whether a time CT,counted by the timer, is larger than a predetermined maximum time dataT_(max) (e.g. 2.0 ms), which is determined on the basis of a controlrange of the exposure factor A_(V)E in the external flash device 100.Note, the maximum time data T_(max) is stored in the EEPROM 124, and isread from the EEPROM 124 in step S102 of the main routine of FIGS. 20and 21.

At step S145, if CT≦T_(max), the control returns to step S143. When thechange of the signal level of input port P7 from the low level [0] tothe high level [1] is confirmed without the counted time CT reaching themaximum time data T_(max), i.e. when the second light-pulse signal,emitted from the built-in flash device 16′ of the camera 10, has beendetected by the light receiving circuit GS (T3 in FIG. 5), the controlproceeds from step S143 to step S144, in which the counted time CT isset as a time interval data TA_(V) between the emissions of the firstand second light-pulse signals from the built-in flash device 16′.

At step S146, it is determined whether the set time interval data TA_(V)is smaller than a predetermined minimum time data T_(min) (e.g. 0.9 ms),which is determined on the basis of the control range of the exposurefactor A_(V)E in the external flash device 100. Note, the minimum timedata T_(min) is also stored in the EEPROM 124, and is read from theEEPROM 124 in step S102 of the main routine of FIGS. 20 and 21.

At step S146, if TA_(V)≧T_(min), the control proceeds to step S147, acorrection data α is added to the time interval data TA_(V). Thecorrection data α is to correct characteristic variations in electronicparts, such as the photo-transistor 138, the capacitors 134 and 134 andso on, of the external flash device 100. Note, the correction data α isalso stored in the EEPROM 124, and is read from the EEPROM 124 in stepS102 of the main routine of FIGS. 20 and 21.

At step S148, the output signal level of the output port P5 isdetermined in accordance with a magnitude of the corrected time intervaldata TA_(V). Also, at step S148, a reference voltage is output to thesecond input terminal (+) of the comparator 145 via the output portP_(da) (S28 in FIG. 5) and a level of the output reference voltage isdetermined in accordance with the magnitude of the corrected timeinterval data TA_(V).

Referring to the table of FIG. 18, a relationship between the timeinterval data TA_(V), the reference voltage and the output signal levelof the output port P6 are shown. Note, in this table, “VA_(V)”represents the reference voltage.

As shown in the table of FIG. 18, when the time interval data TA_(V) isequal to or smaller than “1.5 ms”, the signal level of the output portP5 is caused to be low [0], thereby turning OFF the analog switch 131 sothat an electrical connection is established between the collector ofthe photo-transistor 138 and the capacitor 137 exhibiting the smallcapacitance (of course, provided that P6=1). On the other hand, when thetime interval data TA_(V) is larger than “1.5 ms”, the signal level ofthe output port P5 is caused to be high [1], thereby turning ON theanalog switch 131 so that an electrical connection is establishedbetween the collector of the photo-transistor 138 and both the capacitor136 exhibiting the large capacitance and the capacitor 137 exhibitingthe small capacitance (of course, provided that P6=1). Note, the ratioof the capacitor 137 to the capacitor 136 in capacitance is 1:31, asstated above.

At step S149, it is monitored whether the signal level of the input portP7 is changed from the high level [1] to the low level [0]. When thechange of the signal level of input port P7 from the high level [1] tothe low level [0] is confirmed (T4 in FIG. 5), the control proceeds tostep S150, in which the timer is reset, and is restarted.

At step S151, the signal level of the output port P1 is caused to behigh [1], thereby turning ON the IGBT 117 so that an flash-lightemission of the xenon lamp 115 starts (T5 and S22 in FIG. 5). Note, asalready stated, the time period T_(d1), as shown in FIG. 5, is as veryshort as negligible, and thus the times of T4 and T5 substantiallycoincide with each other.

At step S152, the signal level of the output port P6 is caused to behigh [1], thereby turning ON the analog switch 132 so that an electricconnection is established between the collector of the photo-transistor138 and either only the capacitor 137 or both the capacitors 136 and137. Thus, a part of the flash-light emission of the xenon lamp 115 isdetected as a reflected light by the photo-transistor 138 of the lightreceiver 155, thereby producing a collector current in thephoto-transistor 138 (S10 in FIG. 5), and the produced collector currentis accumulated in either only the capacitor 137 or both the capacitors136 and 137, thereby developing a charge voltage therein. The developedcharge voltage is gradually increased (S25 in FIG. 5), and is input tothe first input terminal (−) of the comparator 145.

At step S153, it is determined whether the signal level of the inputport P8 has been changed from the low level [0] to the high level [1],i.e. it is determined whether the charge voltage, developed in eitheronly the capacitor 137 or both the capacitors 136 and 137 has reachedthe reference voltage VA_(V). When the change of the signal level of theinput port P8 from the low level [0] to the high level [1] is notconfirmed, the control proceeds to step S154, in which it is determinedwhether a time CT, counted by the timer, is larger than a maximumflashing-time data T_(flash) of the external flash device 100.

At step S154, if CT≦T_(flash), the control returns to step S153. Whenthe change of the signal level of input port P8 from the low level [0]to the high level [1] is confirmed without the counted time CT reachingthe maximum charging-time data T_(flash), i.e. when the charge voltage,developed in either only the capacitor 137 or both the capacitors 136and 137 reaches the reference voltage VA_(V) (T6 in FIG. 5), the controlproceeds the control proceeds from step S153 to step S155, in which thesignal level of the output port P1 is caused to be low [0], therebyturning OFF the IGBT 117, resulting in stoppage of the flash-lightemission from the xenon lamp 115.

At step S156, the flag F_(charge) is made to be “0” in order to start anelectrical charging of the main capacitor 109. Then, at step S157, thetimer is stopped and reset.

At step S158, the signal level of each of the output ports P4 and P5 iscaused to be high [1], and the signal level of the output port P6 iscaused to be low [0]. Namely, these output ports are returned to theprevious state prior to the execution of the P7-interruption routine.Then, at step S159, the prohibition of all interruption-processings inthe CPU 123 is released. Thereafter, the control returns to the mainroutine of FIGS. 20 and 21.

At step S145, when the counted time CT reaches the maximum time dataT_(max) without confirming the change of the signal level of input portP7 from the low level [0] to the high level [1], i.e. when the emissionof the second light-pulse signal from the built-in flash device 16′cannot be detected by the photo-transistor 138, the control immediatelyproceeds from step S145 to step S157, and the routine comprising stepsS157, S158 and S159 is executed as mentioned above, resulting indiscontinuance of the execution of the P7-interruption routine.

Also, at step S146, when the set time interval data TA_(V) is smallerthan the minimum time data T_(min) (e.g. 0.9 ms), it is determined thatthe emission of the second light-pulse signal from the built-in flashdevice 16′ is erroneously detected by the photo-transistor 138. Thus,the control immediately proceeds from step S146 to step S157, and theroutine comprising steps S157, S158 and S159 is executed as mentionedabove, resulting in discontinuance of the execution of theP7-interruption routine.

Further, at step S154, when the counted time CT, is larger than themaximum flashing-time data T_(flash) of the external flash device 100,it is determined that the flash-light emission of the external flashdevice 100 is erroneously controlled. Thus, the control immediatelyproceeds from step S154 to step S155, and the routine comprising stepsS155, S156, S157, S158 and S159 is executed as mentioned above,resulting in discontinuance of the execution of the P7-interruptionroutine.

FIG. 25 schematically shows a situation in which the object A isphotographed by a single lens reflex type camera (referred to as SLRcamera hereinafter) 110, using the aforesaid external flash device 100,and a flash-light-emission of the external flash device 100 iscontrolled by a second embodiment of a flash-control system according tothe present invention. In FIG. 25, the elements similar to those of thecamera 10 shown in FIG. 1 are indicated by the same references. Namely,in this drawing, respective references 10 a, 11, 12, 13, 16, 23 and 24indicate a camera body, a flash-mode selection switch button 11, arelease switch button 12, a power ON/OFF switch button 13, aflash-window 16, a lens barrel 23 and a photographing lens system 24,and each of these elements functions in substantially the same manner asmentioned above. Note, in FIG. 25, reference 29 indicates a rotary dialfor manually setting a stop value of a diaphragm of the SLR camera 110.

FIG. 26 schematically shows an block diagram of the SLR camera 110. Inthis drawing, the features similar to those of FIG. 2 are indicated bythe same references.

Similar to the aforesaid LS camera 10, the SLR camera 110 is alsoprovided with a system control circuit 40, which may be constituted as amicrocomputer, used to control the SLR camera 110 as a whole,comprising, a central processing unit (CPU), a read-only memory (ROM)for storing programs and constants, a random-access memory (RAM) forstoring temporary data, and an input/output interface circuit (I/O).

The system control circuit 40 is electrically powered by a battery 70,and the power ON/OFF switch button 13 is associated with a power ON/OFFswitch 13 a, which is turned ON and OFF by manipulating the power switchbutton 13. When the power ON/OFF switch is turned OFF, the CPU of thesystem control circuit 40 is put in a sleep mode in which a powerconsumption is approximately zero, and, when the power ON/OFF switch isturned ON, the CPU of the system control circuit 40 is put in an activemode.

As well known, the SLR camera 110 features a focal-plane shutter,generally indicated by reference 45, which includes an electromagneticleading-shutter-actuating mechanism 45 a, an electromagnetictrailing-shutter-actuating mechanism 45 b, and a shutter driver circuit45 c for driving both the mechanisms 45 a and 45 b under control of asystem control circuit 40. The focal-plane shutter 45 further includes aleading shutter curtain and a trailing shutter curtain actuated by themechanisms 45 a and 45 b, respectively.

Each of the shutter curtains is movable between a first position (i.e.an initial position) and a second position (i.e. an end position), andis associated with a spring such hat each curtain is elastically movedfrom the first position toward the second position. Usually, each of theshutter curtains is constrained by the corresponding mechanism (45 a, 45b) at the first position against the elastic force of the spring. Duringa photographing operation, the leading shutter curtain is released fromthe first position so as to be elastically moved toward the secondposition, thereby opening the focal-plane shutter 45, and then thetrailing shutter curtain is released from the first position so as to beelastically moved toward the second position, thereby closing thefocal-plane shutter 45. Namely, a duration of a shutter-open time isdefined as a duration of time between a time at which the leadingshutter curtain is released from the first position and a time at whichthe trailing shutter curtain is released from the first position.

Also, in the SLR camera 110, the aforesaid diaphragm, which may bemanually operated by the rotary dial 29, is incorporated in aphotographing lens system 24 to adjust an amount of light passingtherethrough. The diaphragm comprises a plurality of blades which areradially and movably arranged so as to define continuously varyingapertures, whereby the amount of light passing through the photographinglens system 24 is adjustable. Usually, an aperture of the diaphragm isrepresented as a stop value. Of course, the larger the aperture of thediaphragm, the smaller the stop value, and vice versa.

The stop value of the diaphragm is adjustable in either an automaticprogram mode or a manual mode.

In the automatic program mode, the diaphragm is actuated by a diaphragmmotor incorporated in the lens barrel 23, and the diaphragm motor isdriven by a diaphragm driver circuit 49 provided in the lens barrel 23.Of course, in the automatic program mode, the diaphragm is automaticallygiven a setting of the stop value, as stated in detail hereinafter.Note, when the lens barrel 23 is attached to the camera body 10 a, asshown in FIG. 25, the diaphragm driver circuit 49 is electricallyconnected to the system control circuit 40.

On the other hand, in the manual mode, the diaphragm is manually given asetting of the stop value by manipulating the rotary dial 29 (FIG. 25).The rotary dial 29 is associated with a manual stop-value setter 29 a(FIG. 26) having a stop-value detector for detecting a stop valuemanually set thereby, and the manual stop-value setter 29 a is connectedto the system control circuit 40 via the stop-value detector. Thus, themanually-set stop value is suitably retrieved as a stop value data bythe system control circuit 40 from the manual stop-value-setter 29 a.

Similar to the aforesaid LS camera 10, the SLR camera 110 is providedwith an internal or built-in flash device, associated with theflash-window 16, which is generally indicated by reference 16′, and thebuilt-in flash device 16′ is electrically powered by the battery 70. Thebuilt-in flash device 16′ is essentially identical to that of FIG. 2.Namely, respective references 16 a, 16 b, 16 c, 16 d and 16 e indicate astep-up transformer circuit, a main capacitor, a flash lamp, such as axenon lamp, a flash-light-emission control circuit, a charge-voltagedetector circuit, and each of these elements functions in essentiallythe same manner as explained with reference to FIG. 2. Also, theflash-light-emission control circuit 16 d has an insulated-gate bipolartransistor (IGBT) incorporated therein to control the energization ofthe flash lamp 16 c, i.e. a turn-ON and a turn-OFF of the flash lamp 16c.

Note, the focal-plane shutter 45 is associated with a shutter switch 33,which is turned ON when the leading shutter curtain reaches the secondposition, i.e. when the focal-plane shutter 45 is fully opened, and theshutter switch 33 is utilized to determine a timing at which aflash-light should be emitted from the built-in flash device, asexplained in detail hereinafter.

Similar to the aforesaid LS camera 10, a back-cover switch 36 is used todetect whether a back-cover of the camera body 10 a is opened or closed,and functions in essentially the same manner as in FIG. 2. Of course,the back-cover switch 36 is associated with a DX code detector circuit26. When it is detected by a change of the back-cover switch 36 from anOFF-state to an ON-state that a film cartridge has been loaded in thecamera 110, a DX code data, representing a sensitivity of a photographicfilm concerned, is read from the loaded film cartridge by the DX codedetector circuit 26, and is then retrieved by the system control circuit40.

Also, the back-cover switch 36 is associated with a film-driver circuit42 for driving a film-feeding motor M1, and the film-driver circuit 42is operated under control of the system control circuit 40. When theloading of the film cartridge, i.e. the change of the back-cover switch36 from the OFF-state to the ON-state is detected by the system controlcircuit 40, the film-driver circuit 42 is operated, thereby driving thefilm-feeding motor M1 such that the film is drawn out of the filmcartridge by a predetermined length, and thus a first frame of the filmis positioned onto a photographing plane.

Of course, similar to the aforesaid LS camera 10, whenever aphotographing operation is completed, the film-feeding motor M1 isautomatically driven by the film-driver circuit 42 such that the film isfed from the film cartridge by one frame length of the film. Namely, afilm-feeding detector circuit 28 is used to detect a feeding of oneframe of the film. When the feeding of one frame of the film is detectedby the film-feeding detector circuit 28, the driving of the film-feedingmotor M1 is stopped.

Similar to the aforesaid LS camera 10, a film-rewinding switch 34 ismanipulated by a film-rewinding switch button, which may be provided ina bottom of the camera body 10 a of the SLR camera 110, and isassociated with the film-driver circuit 42 for driving the film-feedingmotor M1. When the film-rewinding switch 34 is turned ON, thefilm-feeding motor M1 is reversely driven such that the film is forciblyrewound in the film cartridge. Of course, after the last frame of thefilm is exposed by a photographing operation, the film-feeding motor M1is reversely driven for rewinding all the film in the film cartridge.Note, it is detected by the film-feeding detector circuit 28 whether therewinding of the film is completed.

In the SLR camera 110, the release switch button 12 is also associatedwith both a photometry measurement switch 12 a and a release switch 12b. Similar to the aforesaid LS camera 10, when the release switch button12 is partly depressed, the photometry measurement switch 12 a is turnedON, and, when the release switch button 12 is fully depressed, therelease switch 12 b is turned ON.

The photometry measurement switch 12 a is associated with a photometrymeasurement circuit 22 having a photometry measurement sensor. Whenphotometry measurement switch 12 a is turned ON, it detects an intensityof light, reflected from the object A, through the photographing lenssystem 24, thereby producing a luminance signal representing a luminanceof the object A. The respective luminance signal is suitably retrievedas a luminance data by the system control circuit 40.

Further, the photometry measurement switch 12 a is associated with anautomatic-focusing (AF) detector circuit 27 having an image sensor fordetecting a defocus-amount of an image of the object A formed on theimage sensor through the photographing lens system 24, and the detecteddefocus-amount of the image is retrieved as a defocus data from the AFdetector circuit 27 by the system control circuit 40. The AF detectorcircuit 27 is then associated with an AF-driver circuit 43 for drivingan AF-focusing motor M4, and the AF-driver circuit 43 is operated undercontrol of the system control circuit 40 to drive the AF-focusing motorM4, which is associated with an automatic focusing mechanismincorporated in the photographing lens system 24. Whenever thephotometry measurement switch 12 a is turned ON, the automatic focusingmechanism is actuated by driving the AF-focusing motor M4, such that thephotographing lens system 24 is moved from an initial position inaccordance with the retrieved defocus data, thereby properly focusingthe image of the object A on the aforesaid image sensor.

Further, the release switch 12 b is associated with the shutter-drivercircuit 45 c of the focal-plane shutter 45. Namely, when the releaseswitch 12 b is turned ON, the focal-plane shutter 45 is opened over agiven shutter-open time duration by actuating in turn theleading-shutter-actuating mechanism 45 a and thetrailing-shutter-actuating mechanism 45 b. In particular, as statedabove, the leading shutter curtain is released from the first positionso as to be elastically moved toward the second position, therebyopening the focal-plane shutter 45, and then the trailing shuttercurtain is released from the first position so as to be elasticallymoved toward the second position, thereby closing the focal-planeshutter 45.

Similar to the aforesaid LS camera, the flash-mode selection switchbutton 11 is associated with a flash-mode selection switch 11 a, whichis turned ON by a depression of the flash-mode selection switch button11. By manipulating the flash-mode selection switch button 11, one of anautomatic internal flash mode, an internal flash-OFF mode, an internalflash-ON mode and the external flash-ON mode is selected. Namely, aselection of each individual flash mode is sequentially and cyclicallyswitched in a given order by every turning ON of the flash-modeselection switch 11 a.

As shown in FIG. 26, the system control circuit 40 is provided with aself-timer switch 35, which is operated by a self-timer switch buttonprovided at a suitable location on the camera body 10 a of the SLRcamera 110. When the self-timer switch 35 is turned ON, the focal-planeshutter 45 cannot be immediately operated by a turn-ON of the releaseswitch 12 b. Namely, the operation of the focal-plane shutter 45 isdelayed until a given time period, for example, 10 sec elapses after theturn-ON of the release switch 12 b. Also, the system control circuit 40is provided with a self-timer lamp 66, which is blinked ON and OFF whilethe aforesaid given time period elapses.

Further, the system control circuit 40 is provided with a TTL (throughthe lens) light-receiver circuit 44 a, which is utilized to control anamount of a flash-light emission of the built-in flash device 16′ whenthe object A is photographed with the flash-light emission of thebuilt-in flash 16′. The TTL light-receiver circuit 44 a has aphoto-sensor which is arranged such that light, made incident on a filmto be photographed, is sensed as a reflected light by the photo-sensor.Namely, during the flash-light emission of the built-in flash device16′, the light, which passes through the photographing lens system 24,is sensed as a part of the flash-light emission of the built-in flashdevice 16′ by the photo-sensor of the TTL light-receiver circuit 44 a.

As shown in FIG. 26, the TTL light-receiver circuit 44 a is associatedwith an integration circuit 44 b. The light, sensed by the photo-sensorof the TTL light-receiver circuit 44 a, is converted into an electriccharge, and the converted electric charge is accumulated in theintegration circuit 44 b, in which a voltage is developed in accordancewith the accumulation of the electric charge. The developed voltage issuitably retrieved as a voltage data by the system control circuit 40from the integration circuit 44 b. Of course, the retrieved voltage datarepresents a total amount of the light sensed by the photo-sensor of theTTL light-receiver circuit 44 a.

The TTL light-receiver circuit 44 a is also associated with areference-voltage setting circuit 44 c which outputs a reference voltageto the system control circuit 40. In the reference-voltage settingcircuit 44 c, a reference voltage is produced on the basis of a DX codedata, obtained from the DX code detector circuit 26, and so on, and thusthe produced reference voltage corresponds to an amount of a flash-lightto be emitted from the built-in flash device 16′ to photograph theobject with a proper exposure. The produced reference voltage issuitably retrieved as a reference voltage data by the system controlcircuit 40 from the reference-voltage setting circuit 44 c.

During the flash-light emission of the built-in flash device 16′, thevoltage data, representing a total amount of the light sensed by thephoto-sensor of the TTL light-receiver circuit 44 a, is compared withthe reference voltage data obtained from the reference-voltage settingcircuit 44 c. When the voltage data reaches the reference voltage data,the flash-light emission of the built-in flash device 16′ is stopped.

Similar to the aforesaid LS camera 10, the SLR camera 110 is alsoprovided with a liquid crystal display (LCD) 30 which is arranged at asuitable location on the camera body 10 a of the SLR camera 110. Ofcourse, the LCD 30 is operated under control of the system controlcircuit 40, and displays various messages regarding a selected flashmode, a number of frames of a loaded film cartridge and so on.

Similar to the aforesaid first embodiment, when a photographingoperation is performed in the situation as shown in FIG. 25, i.e. whenthe external flash-ON mode and the wireless mode are selected in the SLRcamera 110 and the external flash device 100, respectively, the built-inflash device of the SLR camera 110 is used as a light-signal-producingsource for controlling both an amount of flash-light-emission and aflash-timing of the external flash device 100.

FIG. 27 shows a flowchart of a main routine executed in the systemcontrol circuit 40 of the SLR camera 110. Namely, the SLR camera 110operates in accordance with the main routine. The main routine isexecuted by turning ON the power ON/OFF switch 13 a, and the executionof the main routine is repeated as long as the power ON/OFF switch 13 ais in the ON-state.

At step S1201, the system control circuit 40 is subjected toinitialization. Namely, the system control circuit 40 includes variouselements, such as CPU, RAM, input ports, output ports, registers and soon, and these elements are initialized.

At step S1202, a flag F is made to be “1”. The flag F indicates whetheran electrical charging of the main capacitor 16 b of the built-in flashdevice 16′ is required. Namely, when the charge-requiring flag F isgiven a setting of “1”, the electrical charging of the main capacitor 16b is required, and, when the charge-requiring flag F is given a settingof “0”, the electrical charging of the main capacitor 16 b is notrequired.

At step S1203, it is determined whether the film-rewinding switch 34 hasbeen turned ON. When the turn-ON of the switch 34 is confirmed, thecontrol proceeds to step S1204, in which a forcible-rewinding routine isexecuted. Namely, the film, loaded in the SLR camera 110, is forciblyrewound. Thereafter, the control returns step S1203. Note, it isdetected by the film-feeding detector circuit 28 whether the rewindingof the film has been completed.

At step S1203, if the film-rewinding switch 34 is in the OFF-state, thecontrol proceeds to step S1205, in which it is determined whether achange of the back-cover switch 36 has occurred. When the back-coverswitch 36 has changed from an OFF-state to an ON-state, i.e. when it isreckoned that a loading of a film cartridge has been performed, thecontrol proceeds to step S1206, in which a film-loading/processingroutine, involved in the loading of the film cartridge, is executed.Thereafter, the control returns to step S1203.

In executing the film-loading/processing routine, first, a film counter,contained in the system control circuit 40, is reset to “0” when theback-cover switch 36 is turned OFF (i.e. when the back-cover is opened).Note, a counting result of the film counter is displayed on the LCD 30.Also, the driver circuit 42 is operated, thereby driving thefilm-feeding motor M1 such that the film is drawn out of the filmcartridge by a predetermined length, and thus a first frame of the filmis positioned onto the photographing plane. Further, a DX code data,representing a sensitivity of the film, is read from the loaded filmcartridge by the DX code detector circuit 26.

At step S1205, when a change has not occurred in the back-cover switch36, the control proceeds to step S1207, in which it is determinedwhether the photometry measurement switch 12 a has been turned ON, i.e.whether the release switch button 12 has been partly depressed. When theturn-ON of the photometry measurement switch 12 a is confirmed, thecontrol proceeds to step S1208, in which a photographing operationroutine is executed. Thereafter, the control returns to step S1203.

Of course, as stated above, when the switch 12 a is turned ON, thephotometry measurement circuit 22 are electrically energized. Namely, aluminance of the object A is measured by the photometry measurementcircuit 22, thereby producing a luminance signal in the circuit 22.

Note, the photographing operation routine is explained in detailhereinafter with reference to FIGS. 28 and 29.

At step 1207, when the turn-ON of the photometry measurement switch 12 ais not confirmed, the control proceeds to step S1209, in which it isdetermined whether the charge-requiring flag F is “1” or “0”. If F=1,the control proceeds to step S1210, in which a pre-charging routine, asshown in FIG. 9, is executed for performing the electrical charging ofthe main capacitor 16 b, whereby the built-in flash device 16′ is madeavailable for a flash-light emission, and then the control proceeds tostep S1211. On the other hand, at step S1209, if F=0, the control skipsto step S1211.

In either event, at step S1211, it is determined whether the powerON/OFF switch 13 a has been turned OFF. If the power ON/OFF switch is inthe ON-state, the control returns to step S1203. Namely, as long as thepower ON/OFF switch 13 a is in the ON-state, the routine comprisingsteps S1201 to S1211 is repeated.

At step S1211, when the OFF-state of the power ON/OFF switch 13 a isconfirmed, the control proceeds to step S1212, in which the CPU of thesystem control circuit 40 is put in the sleep mode, and the main routinecannot be executed until the power ON/OFF switch 13 a is turned ON.

FIGS. 28 and 29 show a flowchart of the photographing operation routineexecuted in step S1208 of the main routine of FIG. 27.

At step S1241, it is determined whether the internal flash-OFF mode hasbeen selected. When the selection of the internal flash-OFF mode is notconfirmed, i.e. when a flash-light emission of the built-in flash device16′ is allowed upon photographing, the control proceeds to step S1242,in which an additional-charging routine is executed for performing anadditional-electrical charging of the main capacitor 16 b such that thebuilt-in flash device 16′ is allowed to emit a flash-light in aphotographing operation.

Note, the additional-charging routine, executed at step S1204, issubstantially identical to that shown in FIG. 10, except that: at stepS301, a suitable symbol is displayed on the LCD 30 in a blinking mode,in place of blinking ON and OFF the red lamp 62, thereby announcing thatthe built-in flash device 16′ is in the course of theadditional-electric charging state; at step S309, the display of thesymbol on the LCD 30 is changed from the blinking mode to acontinuously-displayed mode, in place of continuously lighting the redlamp 62, thereby announcing that the additional-charging of the maincapacitor 16 b is properly performed; and, at step 315, the symboldisappears from the LCD 30, in place of turning OFF the red lamp 62,thereby announcing that the additional-charging of the main capacitor 16b is improperly performed.

At step S1243, it is determined whether the additional-charging of themain capacitor 16 b has been properly performed by the execution of theadditional-charging routine. If the additional-charging of the maincapacitor 16 b is improper, the control immediately returns to the mainroutine of FIG. 27.

At step S1243, when the additional-charging of the main capacitor 16 bis proper, the control proceeds to step S1246. Also, at step 1241, whenthe selection of the internal flash-OFF mode is confirmed, i.e. when aflash-light emission of the built-in flash device 16′ is not allowedupon photographing, the control skips to step S1246.

In either event, at step 1246, an automatic focusing (AF) routine isexecuted. In the execution of the AF routine, a defocus data,representing a degree of defocus of an image of the object A to bephotographed, is retrieved from the AF detector circuit 27, and theautomatic focusing mechanism, incorporated in the photographing lenssystem 24, is actuated by driving the AF-focusing motor M4, such thatthe lens system 24 is moved from the initial position in accordance withthe retrieved defocus data, thereby properly focusing the image of theobject A on a photographing plane.

At step S1247, a photometry measurement routine is executed, whereby aluminance signal, representing a luminance of the object A, is retrievedas a luminance data from the photometry measurement circuit 22 by thesystem control circuit 40. Then, at step S1248, an exposure-calculationroutine is executed. By executing the exposure-calculation routine, ashutter speed data for the focal-plane shutter 45 is calculated on thebasis of the retrieved luminance data. Also, when the automatic programmode is selected, a stop value data for the diaphragm is furthercalculated on the basis of the retrieved luminance data.

Note, the exposure-calculation routine is explained in detailhereinafter with reference to FIGS. 30 and 31.

At step S1249, it is determined whether the photometry measurementswitch 12 a is still in the ON-state. When the photometry measurementswitch 12 a is in the ON-state, the control proceeds to step S1251, inwhich it is determined whether the release switch 12 b has been turnedON, i.e. whether the release switch button 12 has been fully depressed.If the release switch 12 b is in the OFF-state, the control returns tostep S1247.

Namely, the routine comprising steps S1247, S1248, S1249 and S1251 isrepeated until the release switch 12 b is turned ON. During theexecution of the routine comprising steps S1247, S1248, S1249 and S1251,if the photometry measurement switch 12 a is turned OFF, i.e. if thepartial depression of the release switch button 12 is emancipated, dueto, for example, the photographing operation concerned being canceled,the control immediately returns to the main routine of FIG. 27.

At step S1251, when the turn-ON of the release switch 12 b is confirmed,the control proceeds to step S1252, in which it is determined whetherthe self-timer switch 35 is in the ON-state. When the turn-ON state ofthe self-timer switch 35 is confirmed, the control proceeds to stepS1253, in which a self-timer/processing routine is executed. In theexecution of the self-timer/processing routine, it is monitored whethera time period of 10 sec has elapsed, and the self-timer lamp 66 isblinked ON and OFF during the time period of 10 sec.

After it is confirmed that the time period of 10 sec has elapsed, theself-timer lamp 66 is turned OFF, and then the control proceeds to step1254. On the other hand, at step S1252, when the turn-ON state of theself-timer switch 35 is not confirmed, the control directly proceedsfrom step S1252 to step 1254.

In either event, at step 1254, it is determined whether the automaticprogram mode is selected. When the selection of the automatic programmode is confirmed, the control proceeds to step S1255, in which astop-value setting routine is executed. In the execution of thestop-value setting routine, the diaphragm is given a setting of thecalculated stop value data, which is obtained by the execution of the anexposure-calculation routine (S1248).

After the setting of the calculated stop value data in the diaphragm,the control proceeds to step S1256. On the other hand, when theselection of the automatic program mode is not confirmed, the controldirectly proceeds from step 1254 to step S1256. Note, of course, whenthe automatic program mode is not selected, a stop value data of thediaphragm is manually set, as stated above.

In either event, at step S1256, an exposure-controlling routine isexecuted. In executing the exposure-controlling routine, the focal-planeshutter 45 is operated in accordance with the calculated shutter speeddata, which is obtained by the execution of the an exposure-calculationroutine (S1248).

Note, the exposure-controlling routine is explained in detail withreference to FIGS. 32, 33 and 34.

After the execution of the exposure-controlling routine, the controlproceeds to step S1257, in which a film-feeding routine is executed. Inthe execution of the film-feeding routine, the film-feeding motor M1 isdriven such that the film is wound on from the film cartridge by alength corresponding to one frame. Then, at step S1258, it is determinedwhether the film has ended. If more film remains, the control returns tothe main routine of FIG. 27. At step S1258, if the end of the film isconfirmed, the control proceeds to step S1259, in which a film-rewindingroutine is executed, whereby the film-feeding motor M1 is reverselydriven until the film is rewound.

FIGS. 30 and 31 show a flowchart of the exposure-calculation routineexecuted in step S1248 of the photographing operation routine of FIGS.28 and 29.

At step S1331, it is determined whether the automatic program mode isselected. When the automatic program mode is not selected, i.e. when themanual mode is selected, the control proceeds to step S1332, in which astop value data A_(V) is retrieved from the manual stop-value-setter 29a. Then, at step S1333, a shutter speed data T_(V) is calculated, usingthe retrieved stop value data A_(V), on the basis of the APEX system.Namely, the calculation of the shutter speed data T_(V) is based on thefollowing equation:

T _(V) =B _(V) +S _(V) −A _(V)

Herein: of course, B_(V) represents the luminance data retrieved fromthe photometry measurement circuit 22 (S1247); and S_(V) represents theDX code data or sensitivity of the photographic film concerned detectedby the DX code detector circuit 26 (S1206).

At step S1334, it is determined whether the internal flash-OFF mode isselected. When the internal flash-OFF mode is selected, i.e. when thebuilt-in flash device 16′ is not allowed to emit a flash-light uponphotographing, the control immediately returns to the photographingoperation routine of FIGS. 28 and 29.

On the other hand, when the internal flash-OFF mode is not selected,i.e. when the built-in flash device 16′ is allowed to emit a flash-lightupon photographing (e.g. the internal flash-ON mode or the externalflash-ON mode), the control proceeds from step S1334 to step S1335, inwhich it is determined whether the calculated shutter speed data T_(V)is larger than a flash-synchronous shutter speed data T_(VS).

Note, the flash-synchronous shutter speed data T_(VS) is defined as afastest shutter speed that ensures a full opening of the focal-planeshutter 45. In other words, such a shutter speed may be defined as atime period counted from a time, at which the leading shutter curtain isreleased from the first position, to a time, at which the trailingshutter curtain is released from the first position which occurs as soonas the leading shutter curtain reaches the second position. Usually, theflash-synchronous shutter speed data T_(VS) may be a shutter speed of{fraction (1/125)} sec.

At step S1335, if T_(V)>T_(VS), the control proceeds to step S1336, inwhich the calculated shutter speed data T_(V) is given a setting of theflash-synchronous shutter speed data T_(VS). Namely, whenever thecalculated shutter speed data T_(V) is larger than the flash-synchronousshutter speed data T_(VS), the calculated shutter speed data T_(V) ishandled as the flash-synchronous shutter speed data T_(VS). Thereafter,the control returns to the photographing operation routine of FIGS. 28and 29.

On the other hand, at step S1335, if T_(V)≦T_(VS), the controlimmediately returns to the photographing operation routine of FIGS. 28and 29. In this case, of course, the calculated shutter speed data T_(V)is handled as it stands.

At step S1331, when the automatic program mode is selected, the controlproceeds to step S1338, in which a stop value data A_(V) and a shutterspeed data T_(V) are calculated on the basis of the luminance dataB_(V), retrieved from the photometry measurement circuit 22 (S1247), andthe DX code data S_(V) or sensitivity of the photographic filmconcerned, detected by the DX code detector circuit 26 (S1206).

At step S1339, it is determined whether the internal flash-OFF mode isselected. When the internal flash-OFF mode is selected, i.e. when thebuilt-in flash device 16′ is not allowed to emit a flash-light uponphotographing, the control immediately returns to the photographingoperation routine of FIGS. 28 and 29.

On the other hand, when the internal flash-OFF mode is not selected,i.e. when the built-in flash device 16′ is allowed to emit a flash-lightupon photographing (e.g. the internal flash-ON mode or the externalflash-ON mode), the control proceeds from step S1339 to step S1340, inwhich it is determined whether the calculated shutter speed data T_(V)is larger than the flash-synchronous shutter speed data T_(VS) asdefined above.

At step S1340, if T_(V)>T_(VS), the control proceeds to step S1341, inwhich the calculated shutter speed data T_(V) is given a setting of theflash-synchronous shutter speed data T_(VS). Namely, whenever thecalculated shutter speed data T_(V) is larger than the flash-synchronousshutter speed data T_(VS), the calculated shutter speed data T_(V) ishandled as the flash-synchronous shutter speed data T_(VS). Then, atstep 1342, the calculated shutter speed data T_(V) is revised on thebasis of the change of the calculated shutter speed data T_(V) into theflash-synchronous shutter speed data T_(VS). Thereafter, the controlreturns to the photographing operation routine of FIGS. 28 and 29.

On the other hand, at step S1340, if T_(V)≦T_(VS), the controlimmediately returns to the photographing operation routine of FIGS. 28and 29. In this case, of course, the calculated shutter speed data T_(V)is handled as it stands.

FIGS. 32, 33 and 34 show a flowchart of the exposure-controlling routineexecuted in step S1256 of the photographing operation routine of FIGS.28 and 29.

At step S1401, a duration of shutter-open time T_(TV) for focal-planeshutter 45 is calculated on the basis of the shutter speed data T_(V)obtained by the execution of the exposure-calculation routine of FIGS.30 and 31. Then, at step S1402, the calculated shutter-open durationtime T_(TV) is set in a first timer TM1, and a time-counting is startedby the first timer TM1. Subsequently, at step S1403, the leading shuttercurtain of the focal-plane shutter 45 is released from the firstposition so as to be elastically moved toward the second position,thereby opening the focal-plane shutter 45.

Note, the first timer TM1 may be defined in the system control circuit40, and is utilized to count shutter-open duration time T_(TV).

At step S1404, it is determined whether the internal flash-OFF mode hasbeen selected. When the selection of the internal flash-OFF mode isconfirmed, i.e. when a flash-light emission of the built-in flash device16′ is not allowed upon photographing, the control jumps to step S1423,in which it is monitored whether the shutter-open duration time T_(TV)has been counted by the first timer TM1. When it is confirmed that theshutter-open duration time T_(TV) has been counted by the first timerTM1, the control proceeds to step S1424, in which the trailing shuttercurtain is released from the first position so as to be elasticallymoved toward the second position, thereby closing the focal-planeshutter 45. Thereafter, the control returns to the photographingoperation routine of FIGS. 28 and 29.

At step S1404, when the selection of the internal flash-OFF mode is notconfirmed, i.e. when a flash-light emission of the built-in flash device16′ is allowed upon photographing, the control proceeds to step S1405,in which it is monitored whether the shutter switch 33 has been turnedON. When the turn-ON of the shutter switch 33 is confirmed, i.e. when itis confirmed that the leading shutter curtain has reached the secondposition, the control proceeds to step S1406, in which it is determinedwhether the external flash-ON mode is selected.

At step S1406, when the external flash-ON mode is not selected, i.e.when the object A is photographed with a flash-light emission of thebuilt-in flash 16′, the control proceeds to step S1416, in which areference voltage is produced in the reference-voltage setting circuit44 c on the basis of the DX code data, detected by the DX code detectorcircuit 26, and so on, and is retrieved as a reference voltage data RVby the system control circuit 40 from the reference-voltage settingcircuit 44 c. Note, as stated above, the produced reference voltagecorresponds to an amount of a flash-light to be emitted from thebuilt-in flash device 16′ to photograph the object A with a properexposure.

At step S1417, a suitable time period of, for example, 5 ms is set in asecond timer TM2, and a time-counting is started by the second timerTM2. Then, at step S1418, a trigger signal is output from the systemcontrol circuit 40 to the IGBT of the flash-light-emission controlcircuit 16 d, thereby turning ON the IGBT, resulting in energization ofthe xenon lamp 16 c by discharging the electrical charges from the maincapacitor 16 b.

Thus, a flash-light emission of the built-in flash device 16′ isstarted, whereby a part of the flash-light emission of the built-inflash device 16′ is detected as a reflected light by the photo-sensor ofthe TTL light-receiver circuit 44 a, resulting in development of avoltage in the integration circuit 44 b, and the developed voltage isretrieved as a voltage data DV by the system control circuit 40 from theintegration circuit 44 b.

At step S1419, it is determined whether the time period of 5 ms has beencounted by the second timer TM2. When the counted time of the secondtimer TM2 has not reached the time period of 5 ms, the control proceedsto step S1420, in which it is determined whether the retrieved voltagedata DV has reached the reference voltage RV obtained from thereference-voltage setting circuit 44 c. If the retrieved voltage data DVhas not reached the reference voltage RV, the control returns to stepS1419.

Namely, the routine comprising steps S1419 and S1420 is repeated untileither the time period of 5 ms has been counted by the second timer TM2or the retrieved voltage data DV has reached the reference voltage RV.When the time period of 5 ms has been counted by the second timer TM2,or when the retrieved voltage data DV has reached the reference voltageRV, the control proceeds to step S1421, in which the flash-lightemission of the built-in flash device 16′ is stopped.

Note, the setting of 5 ms in the second timer TM2 is selected as a timelong enough to control an amount of the flash-light emission of thebuilt-in flash device 16′. Thus, even if the TTL light-receiver circuit44 a fails to properly detect the light-flash emission of the built-inflash device 16′, so that the retrieved voltage data DV cannot reach thereference voltage RV, the flash-light emission of the built-in flashdevice 16′ is forcibly stopped after the time period of 5 ms haselapsed.

After the flash-light emission of the built-in flash device 16′ isstopped, the control proceeds from step S1421 to step S1422, in whichthe charge-requiring flag F is made to be “1”. Then, at step S1423, itis monitored whether the shutter-open duration time T_(TV) has beencounted by the first timer TM1. When it is confirmed that theshutter-open duration time T_(TV) has been counted by the first timerTM1, the control proceeds to step S1424, in which the trailing shuttercurtain is released from the first position so as to be elasticallymoved toward the second position, thereby closing the focal-planeshutter 45. Thereafter, the control returns to the photographingoperation routine of FIGS. 28 and 29.

At step S1406, when the external flash-ON mode is selected, the controlproceeds to step S1407, in which a trigger signal is output from thesystem control circuit 40 to the IGBT of the flash-light-emissioncontrol circuit 16 d, thereby turning ON the IGBT, resulting inenergization of the xenon lamp 16 c by discharging the electricalcharges from the main capacitor 16 b. Thus, a flash-light emission ofthe built-in flash device 16′ is started.

Then, at step S1408, it is monitored whether a very short time of, forexample, 100 μs has elapsed. When it is confirmed that the very shorttime of 100 μs has elapsed, the control proceeds to step S1409, in whichthe outputting of the trigger signal from the system control circuit 40to the IGBT of the flash-light-emission control circuit 16 d is stopped,thereby turning OFF the IGBT, resulting in de-energization of the xenonlamp 16 c. Thus, the flash-light emission of the built-in flash device16′ is stopped.

In short, the flash-light emission of the built-in flash device 16′ iscontinued over the very short time of 100 μs, and is thus received as afirst light-pulse signal by the external flash device 100.

At step S1410, it is determined whether a time period, corresponding atime interval data TA_(V), has elapsed. Note, the time interval dataTA_(V) is calculated as an exposure factor to be transmitted to theexternal flash device 100, on the basis of the calculated stop valuedata A_(V) obtained by the exposure-calculation routine of FIGS. 30 and31. Note, the calculation of the time interval data TA_(V) may beperformed by referring to, for example, a look-up table based on arelationship between stop value data (A_(V)) and time interval data(TA_(V)) and included in the system control circuit 40.

At step S1410, when it is confirmed whether the time period,corresponding the time interval data TA_(V), has elapsed, the controlproceeds to step S1411, in which a trigger signal is again output fromthe system control circuit 40 to the IGBT of the flash-light-emissioncontrol circuit 16 d, thereby turning ON the IGBT, resulting inenergization of the xenon lamp 16 c by discharging the electricalcharges from the main capacitor 16 b. Thus, a flash-light emission ofthe built-in flash device 16′ is again started.

Then, at step S1412, it is monitored whether a very short time of, forexample, 100 μs has elapsed. When it is confirmed that the very shorttime of 100 μs has elapsed, the control proceeds to step S1413, in whichthe outputting of the trigger signal from the system control circuit 40to the IGBT of the flash-light-emission control circuit 16 d is stopped,thereby turning OFF the IGBT, resulting in de-energization of the xenonlamp 16 c. Thus, the flash-light emission of the built-in flash device16′ is stopped.

In short, the second flash-light emission of the built-in flash device16′ is also continued over the very short time of 100 μs, and is thusreceived as a second light-pulse signal by the external flash device100.

Then, at step S1422, the charge-requiring flag F is made to be “1”.Subsequently, at step S1423, it is monitored whether the shutter-openduration time T_(TV) has been counted by the first timer TM1. When it isconfirmed that the shutter-open duration time T_(TV) has been counted bythe first timer TM1, the control proceeds to step S1424, in which thetrailing shutter curtain is released from the first position so as to beelastically moved toward the second position, thereby closing thefocal-plane shutter 45. Thereafter, the control returns to thephotographing operation routine of FIGS. 28 and 29.

As is apparent from the exposure-controlling routine of FIG. 32, theemission of the first and second light-pulses from the built-in flashdevice 16′ is performed just after the shutter switch 33 has been turnedON (S1405), i.e. after the leading shutter curtain has reached thesecond position. This is because a time period for the movement of theleading shutter curtain from the first position to the second positionis not necessarily constant.

Of course, when the first and second light-pulse signals are received bythe external flash device 100, a flash-light is emitted from theexternal flash device 100 in substantially the same manner as mentionedhereinbefore. Namely, the second light-pulse serves as a trigger signalfor initiating the flash-light emission of the external flash device100, and a total amount of the flash-light emission of the externalflash device 100 corresponds to the time interval data TA_(V) betweenthe emissions of the first and second light-pulse signals.

In the aforesaid second embodiment, a timing of the flash-light emissionof the external flash device 100 is somewhat postponed from the time atwhich the focal-plane shutter 45 is fully opened, i.e. at which theshutter switch 33 is turned ON (S1405). Namely, the timing of theflash-light emission of the external is postponed for a timecorresponding to the time interval data TA_(V). Nevertheless, thispostponement is negligible, because the time interval data TA_(V) is setwithin a range of 2 ms, and because a longest flash-light emission timeof the external flash device 100 is 5 ms. In short, the total time 7 msis substantially smaller than the aforesaid flash-synchronous shutterspeed T_(VS) ({fraction (1/125)} sec).

As is apparent from the foregoing, according to the flash control systemof the present invention, when a wireless mode is selected in anexternal flash device, an exposure factor or stop value, necessary tophotograph an object with a proper exposure, can be transmitted from acamera to the external flash device. Thus, a flash-light emission of theexternal flash device in the wireless mode can be properly controlled.

Finally, it will be understood by those skilled in the art that theforegoing description is of preferred embodiments of the system, andthat various changes and modifications may be made to the presentinvention without departing from the spirit and scope thereof.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 11-076232 (filed on Mar. 19, 1999) which isexpressly incorporated herein, by reference, in its entirety.

What is claimed is:
 1. A flash control system for remotely controllingan external flash device by a camera associated with said external flashdevice, said system comprising: a stop value calculator, incorporated insaid camera, that calculates a stop value as an exposure factor for saidexternal flash device; a light signal source, incorporated in saidcamera, that emits a light signal; a light signal controller,incorporated in said camera, that controls said light signal source toemit at least two light signals therefrom at a time interval such thatsaid stop value is represented by said time interval between said atleast two light signals; a light signal detector, incorporated in saidexternal flash device, that detects said at least two light signalsemitted from said light signal source; and a flash-light emissioncontroller, incorporated in said external flash device, that controls anamount of flash-light emission of said external flash device inaccordance with said time interval between said at least two lightsignals.
 2. A flash control system as set forth in claim 1, wherein thecalculation of said stop value by said stop value calculator is based onat least a photometry measurement performed by said camera uponphotographing.
 3. A flash control system as set forth in claim 1,wherein said light signal source comprises a flash lamp of a built-inflash device incorporated in said camera.
 4. A flash control system asset forth in claim 1, further comprising a flash-light emission timingcalculator, incorporated in said camera, that calculates a flash-lightemission timing at which a flash-light should be emitted from saidexternal flash device, wherein said light signal controller furthercontrols an emission of one of said at least two light signals such thatsaid flash-light emission timing is represented by the emission of saidone of said at least two light signals, and said flash-light emissioncontroller further controls a timing of the flash-light emission of saidexternal flash device in accordance with the emission of said one ofsaid at least two light signals.
 5. A flash control system as set forthin claim 4, wherein the control of the timing of the flash-lightemission of said external flash device by said flash-light emissioncontroller is based on a last light signal of said at least two lightsignals.
 6. A flash control system as set forth in claim 1, wherein saidflash-light emission controller includes: a light detector that detectsthe flash-light emission of said external flash device as a reflectedlight; a first processor that processes the reflected light, detected bysaid light detector, to produce a first light-quantitative datarepresenting an amount of the reflected light; a second processor thatprocesses said time interval to produce a second light-quantitative dataderiving from said stop value; and a comparator that compares said firstlight-quantitative data with said second light-quantitative data, suchthat the flash-light emission of said external flash device is stoppedwhen it is determined by said comparator that the first-quantitativedata coincides with said second light-quantitative data.
 7. A flashcontrol system as set forth in claim 6, wherein said light detectorcomprises said light signal detector for detecting said at least twolight signals.
 8. An external flash device comprising: a flash lamp thatemits a flash-light; a light signal detector that detects two lightsignals emitted at a time interval representing a stop value as aphotographic exposure factor; and a flash-light emission controller thatcontrols an amount of a flash-light emission of said flash lamp inaccordance with said time interval between said at least two lightsignals.
 9. An external flash device as set forth in claim 8, furthercomprising a timing controller that controls a timing of the flash-lightemission of said flash lamp on the basis of a detected-timing at whichone of said at least two light signals is detected by said light signaldetector.
 10. An external flash device as set forth in claim 9, whereinthe control of the timing of the flash-light emission of said flash lampby said flash-light emission controller is based on a last light signalof said at least two light signals.
 11. An external flash device as setforth in claim 8, wherein said flash-light emission controller includes:a light detector that detects the flash-light emission of said externalflash device as a reflected light; a first processor that processes thereflected light, detected by said light detector, to produce a firstlight-quantitative data representing an amount of the reflected light; asecond processor that processes said time interval to produce a secondlight-quantitative data deriving from said stop value; and a comparatorthat compares said first light-quantitative data with said secondlight-quantitative data, such that the flash-light emission of saidflash lamp is stopped when it is determined by said comparator that thefirst-quantitative data coincides with said second light-quantitativedata.
 12. An external flash device as set forth in claim 11, whereinsaid light detector comprises said light signal detector for detectingsaid at least two light signals.
 13. A camera comprising: a stop valuecalculator that calculates a stop value as a photographic exposurefactor for an external flash device; a light signal source that emits alight signal to said external flash device; and a light signalcontroller that controls said light signal source to emit at least twolight signals therefrom at a time interval such that said stop value isrepresented by said time interval between said at least two lightsignals.
 14. A camera as set forth in claim 13, wherein said lightsignal source comprises a flash lamp of a built-in flash deviceincorporated in said camera.
 15. A camera as set forth in claim 13,wherein the calculation of said stop value by said stop value calculatoris based on at least a photometry measurement performed by said cameraupon photographing.
 16. A camera as set forth in claim 13, furthercomprising a flash-light emission timing calculator that calculates aflash-light emission timing at which a flash-light should be emittedfrom said external flash device, wherein said light signal controllerfurther controls the emission of said at least two light signals suchthat said flash-light emission timing is represented by an emission ofone of said at least two light signals.
 17. A flash control system asset forth in claim 16, wherein the control of the emission of said atleast two light signals by said light signal controller is performedsuch that said flash-light emission timing is represented by an emissionof a last light signal of said at least two light signals.
 18. A cameraas set forth in claim 17, wherein said camera comprises a lens shuttertype camera, and a timing of the emission of the last light signal ofsaid at least two light signals coincides with a time at which anaperture of a shutter of said lens shutter type camera reaches a maximumaperture during an opening-action of said shutter.
 19. A camera as setforth in claim 17, wherein said camera comprises a single lens reflextype camera, and a timing of an emission of a first light signal of saidat least two light signals coincides with a time, at which a leadingshutter curtain of a focal-plane shutter of said single lens reflex typecamera reaches an end position thereof.